Do I even need this? I just work out a few times a week.

It depends what you're doing. For short, easy sessions you're usually fine on your own stores and water. It earns its place two ways: on longer or harder efforts (about 60–90 minutes and up), where you'd otherwise run your carbohydrate tank toward empty and 'bonk'; and in the gym, where carbs during training help you hit more quality sets and blunt the post-exercise cortisol spike. See 'Does it actually help me build muscle?' below for the honest version of the lifting evidence.

Does it actually help me build muscle?

Honest answer: carbs help you train, but they're not a muscle-builder on their own. Taking carbohydrate during hard training blunts the post-exercise rise in cortisol — your main catabolic, or muscle-breakdown, hormone. In a 12-week study in untrained men (Bird, Tarpenning & Marino, European Journal of Applied Physiology, 2006), the carbohydrate group's cortisol fell after training while the placebo group's rose. That's a real anticatabolic effect. The catch: in that same study the clear muscle-growth and lower-breakdown results came from carbs PLUS protein, not carbs alone — and the most rigorous recent review (Henselmans, Vårvik & Izquierdo, Sports Medicine, 2026, 11 trials) found no significant effect of carbohydrate intake on muscle size once protein is accounted for ('SMD = 0.15, p = 0.23'). So: use it to fuel and recover from hard lifting, pair it with protein for muscle, and don't expect the drink alone to do the building. Both studies are linked in the references below.

Isn't this just expensive sugar water?

It's sugar and salt, deliberately. The carbohydrate is a 2:1 glucose-to-fructose blend so your gut can absorb more of it per hour, and the sodium is in a form the carbohydrate actively helps carry into your body, pulling water in with it. That pairing is what makes it work — and at about 60 cents a serving, it's the opposite of expensive.

Why a 2:1 glucose-to-fructose ratio?

Glucose and fructose are absorbed by two different routes in your gut, so using both lets you take in more total carbohydrate per hour than glucose alone, with less stomach upset. 2:1 is the blend endurance research keeps landing on — a proven default and a low-risk place to start. You don't need to optimize it.

How do carbs help deliver the sodium?

Glucose and sodium cross your gut wall together through the same tiny pump — neither goes through well alone, but paired up they're absorbed quickly, and water follows them in. So the carbohydrate isn't just fuel; it's the ride that carries the sodium and the water into your body. It's the same principle behind medical rehydration drinks.

Why not just take salt tablets and eat sugar separately?

You could, but they do their best work together: the carbohydrate is what helps the sodium and water get absorbed. Putting both in one drink, in the right amounts, is simpler, gentler on your stomach, and means you actually get the teamwork instead of two half-measures.

How much should I take per hour?

Trained athletes commonly target 60–90 g of carbohydrate per hour, which is 1–3 servings of Bonk Juice depending on how long and hard you're going. Your real ceiling depends on how practiced your gut is, so start at the low end and build up gradually rather than maxing out on day one.

How much water do I mix it with?

One serving in 500–750 ml of water. That range keeps the drink close to the concentration of your own blood ('isotonic'), so it leaves your stomach quickly and is comfortable to drink for hours.

Is the citric acid bad for my teeth?

Acids, including the citric acid that gives the drink its tang, can wear at tooth enamel over time — true of any citrusy or sports drink. Rinse with plain water after fueling and avoid brushing immediately afterward. It's a general care note, not a unique downside.

Sports nutrition, from zero

Never thought about fueling? Start here.

If you train but have never treated food as part of your fitness, this is for you. In about five minutes and zero jargon, you’ll learn why you run out of gas, what actually fixes it, and why Bonk Juice’s simple mix is a smart place to begin. No biochemistry degree required — we explain every term as we go.

01What “bonking” is
02Why carbs are the fuel
03Two sugars, two doors
04Why salt matters
05How carbs carry the salt in
06How to actually use it

Shop the fuel Build your plan →

01 · The problem

First: what “bonking” actually is

It's the moment the tank hits empty — and it has a simple cause.

Maybe you’ve felt it on a long run or a hard ride: an hour or two in, your legs turn to concrete, your pace falls off a cliff, and even thinking gets foggy. Cyclists call it bonking; runners call it hitting the wall. It’s not weakness or lack of fitness. It’s an empty fuel tank.

Your body stores fuel two ways. There’s fat — a huge tank, but slow to burn — and carbohydrate (stored in your muscles and liver as something called glycogen) — a much smaller tank, but fast and clean-burning. The harder you push, the more your body leans on that small, fast carbohydrate tank.

Think of it like your phone battery. Most people carry only about 90 minutes of hard effort worth of stored carbohydrate. Push hard with no top-up and you drain to 0% — and a phone at 0% doesn’t run, no matter how good it is.

The fix is almost insultingly simple: eat carbohydrate while you move — plug in the charger before you hit empty, not after. Everything else on this page is just about doing that well.

02 · The fuel

Why carbohydrate is the thing to replace

Of everything you could put in your body mid-effort, carbs are what move the needle.

During easy activity your body is happy burning mostly fat. But as the effort ramps up — a tempo run, a climb, the back half of a race — it shifts to burning carbohydrate, because carbohydrate delivers energy faster and with less oxygen. That’s exactly the fuel that’s in short supply. So the fuel you’re burning fastest is the one you have the least of.

That’s why endurance fueling is mostly about carbohydrate. Protein and fat matter for recovery and everyday health, but mid-effort they’re slow and beside the point. Topping up carbohydrate is what keeps the lights on.

When does this matter? Under ~60–90 minutes, your stored fuel and plain water usually cover you. Past that — or any time you’re going hard — taking in carbohydrate as you go is what separates a strong finish from a death march.

So the question becomes: how do you get carbohydrate into your body, fast enough to matter, without wrecking your stomach? That turns out to be the whole game — and it’s where most of the science lives.

03 · The bottleneck

Two sugars, two doors — so more fuel gets in

The limit isn't your legs. It's how fast your gut can absorb the carbs you swallow.

Here’s the catch nobody tells you: you can swallow carbohydrate faster than your body can actually absorbit. Pour in more than your gut can pass through, and the excess just sits in your stomach and sloshes — that bloated, queasy feeling that ends long days early. So the real skill isn’t cramming in more sugar. It’s helping your gut absorb more of what you take.

The trick is using two different sugars. Glucose and fructoseare absorbed through two separate routes in your gut wall — they’re built a little differently, so each sugar needs its own kind of door. Think of them as two different doors. Lean on glucose alone and everything queues at one door; it jams, and the leftovers slosh. Send glucose and fructose together and you open two doors at once — more total carbohydrate gets through every hour, with far less stomach trouble.

Bonk Juice uses a 2:1 ratio — about two parts glucose to one part fructose. Why roughly twice as much glucose? The glucose door moves carbohydrate faster than the fructose door, so a 2:1 split keeps both doors busy without overloading either. You don’t need to memorize or optimize that number: it’s the blend endurance research keeps landing on, which makes it a proven, low-risk place to start. Each serving gives you 30 g of carbohydrate in exactly that ratio.

Trained athletes aim for 60–90 g of carbohydrate per hour. But your personal ceiling is set by your gut, and a gut is trainable — the more you practice fueling, the more it can take. Start low and build.

Train your gut

Roughly how much carbohydrate the gut can absorb per hour, by how much you’ve practiced (g/hr):

Brand new to fueling~30
Most people, day one
A few weeks of practice~60
Gut starts adapting
Seasoned endurance athlete~90
Months of habit
Elite, years of practice~120
The top end

The takeaway: don’t max out on day one. Build the number up in training, like any other adaptation.

04 · The salt

Why a fuel drink needs salt, not just water

Sweat is salty for a reason — and replacing the water without the salt only half-works.

Taste your sweat sometime — it’s salty. That salt is mostly sodium, and you lose a surprising amount of it on a long, hot effort. Here’s the part that trips people up: if you replace only the waterand not the sodium, you actually dilute what’s left in your body — and it often just gets passed as urine instead of absorbed. Plain water alone can run right through you.

Sodium is what tells your body to take the water in and keep it. It helps pull fluid across your gut wall and helps you hold onto it through hours of work. That’s why every serious sports drink has sodium in it — and why a little salt is the difference between drinking and actually hydrating.

Each serving of Bonk Juice has 350 mg of sodium, plus small amounts of potassium and magnesium — the other salts you sweat out. The goal is simple: make every sip do more than water can.

Per serving · the salts

Sodium350 mg
The one that matters most. Helps your body absorb water and hold onto it instead of passing it straight through.
PotassiumA little
Sodium's partner. The two sit on opposite sides of your muscle and nerve cells, and the balance between them is what lets muscles contract and nerves fire. You sweat some out, so a little goes back in.
MagnesiumA little
Helps muscles relax after they contract, and helps your cells turn fuel into usable energy. You lose small amounts in sweat, so a small amount is included.

05 · The clever part

The carbs carry the salt — and the water — in with them

This is the bit most people never learn, and it's why carbs and sodium belong in the same bottle.

Remember that “door” glucose uses to get into your body? The main one is a tiny pump in your gut wall (scientists call it SGLT1— you can forget the name). Here’s the beautiful catch: that pump only opens when it grabs a glucose anda sodium at the same time. They go through together, hand in hand. One won’t cross without the other.

Think of it as a buddy pass: the glucose can’t get through the door alone, and neither can the sodium — but together they walk right in. And through a process called osmosis — water naturally moving toward the saltier side — water follows them straight across.

So the carbohydrate in your drink isn’t just fuel. It’s the ride that carries the sodium — and the water — into your body. Carbs and sodium together get absorbed far faster than either one alone. This is the exact trick behind the rehydration drinks hospitals use: a little sugar with the salt, because the sugar is what makes the salt and water actually go in.

In one picture

glucose + sodium → through the gut door together → water follows

That’s the whole reason Bonk Juice puts the right carbs and the right sodium in one mix instead of selling you sugar and salt tablets separately. They do their best work as a team.

06 · A small detail that matters

Why the salt is “citrate,” not just table salt

Same sodium, gentler delivery — so you'll actually want to keep drinking it.

There’s more than one way to put sodium in a drink. Bonk Juice uses mostly sodium citrate (sodium attached to citrate, which comes from citrus) plus a measured pinch of table salt, and a little citric acid for a clean citrus tang. It’s the same sodium your body needs — just delivered in a form that’s gentler on your stomach and your taste buds. That’s not vanity: the drink you actually enjoy is the one you’ll finish, and only finished fluid helps.

Easier on the stomach

Citrate keeps the drink close to “isotonic” — about the same concentration as your own blood — so it leaves the stomach quickly instead of sitting heavy.

Tastes cleaner

Citrate is far less harshly salty than table salt, so you get your sodium without the drink tasting like seawater. You finish it — and the fluid you finish is the only fluid that helps.

Nothing exotic

It's the same sodium form used in most sports drinks on the shelf. Not a gimmick — just the version that mixes and tastes best.

One honest caveat

Acids — including the citric acid that makes the drink taste good — can wear at tooth enamel over time, like any citrusy drink. Rinse with plain water after fueling and don’t brush right away. This is a care note, not a benefit.

07 · Using it

How to actually use it

No ritual, no spreadsheet. Three habits and you're fueling like you mean it.

01
Mix
One serving (30 g of carbs) in a 500–750 ml bottle of water. Shake. That amount of water keeps it easy to drink and quick to leave your stomach.
02
Sip
Drink steadily — small sips every 10–15 minutes — rather than chugging it all at once. On long efforts, aim for 1–3 servings an hour.
03
Build up
Start at the low end and practice in training. Your gut adapts. And never try something brand new on race day — rehearse it first.

Want exact numbers for your event?

The calculator turns all of this into a simple, minute-by-minute plan for your weight, sport, and conditions.

Build my plan →

08 · The whole point

So why Bonk Juice — especially if you're just starting?

Because the recipe that works is short, and we sell exactly that, cheaply.

Notice what you just learned. The science of not bonking really comes down to a few things:

Carbohydrate is the fuel you run out of — so you replace it as you go.
Two sugars (2:1 glucose to fructose) let your gut absorb more, with less stomach trouble.
Sodium is what makes the water actually absorb and stay.
The carbs carry the sodium and water in with them — they work as a team.

That’s the entire job. Bonk Juice is exactly that and nothing else — 30 g of carbohydrate in a 2:1 blend, with sodium in the form that rides in with it, at about 60 cents a serving. No rotating flavors to chase, no pro-team logos to pay for, no glossy box. Just the proven essentials.

If you’re new to fueling, that simplicity is the point. You don’t need a shelf of gels and tablets to start — you need the right carbs and the right salt, together, that you’ll actually drink. Get this habit down first. It’s the highest-value, lowest- cost change most people can make to how they feel at hour two.

Shop the fuel — from $9 Build your plan →

09 · Questions

The questions a beginner actually asks

Do I even need this? I just work out a few times a week.: It depends what you're doing. For short, easy sessions you're usually fine on your own stores and water. It earns its place two ways: on longer or harder efforts (about 60–90 minutes and up), where you'd otherwise run your carbohydrate tank toward empty and 'bonk'; and in the gym, where carbs during training help you hit more quality sets and blunt the post-exercise cortisol spike. See 'Does it actually help me build muscle?' below for the honest version of the lifting evidence.
Does it actually help me build muscle?: Honest answer: carbs help you train, but they're not a muscle-builder on their own. Taking carbohydrate during hard training blunts the post-exercise rise in cortisol — your main catabolic, or muscle-breakdown, hormone. In a 12-week study in untrained men (Bird, Tarpenning & Marino, European Journal of Applied Physiology, 2006), the carbohydrate group's cortisol fell after training while the placebo group's rose. That's a real anticatabolic effect. The catch: in that same study the clear muscle-growth and lower-breakdown results came from carbs PLUS protein, not carbs alone — and the most rigorous recent review (Henselmans, Vårvik & Izquierdo, Sports Medicine, 2026, 11 trials) found no significant effect of carbohydrate intake on muscle size once protein is accounted for ('SMD = 0.15, p = 0.23'). So: use it to fuel and recover from hard lifting, pair it with protein for muscle, and don't expect the drink alone to do the building. Both studies are linked in the references below.
Isn't this just expensive sugar water?: It's sugar and salt, deliberately. The carbohydrate is a 2:1 glucose-to-fructose blend so your gut can absorb more of it per hour, and the sodium is in a form the carbohydrate actively helps carry into your body, pulling water in with it. That pairing is what makes it work — and at about 60 cents a serving, it's the opposite of expensive.
Why a 2:1 glucose-to-fructose ratio?: Glucose and fructose are absorbed by two different routes in your gut, so using both lets you take in more total carbohydrate per hour than glucose alone, with less stomach upset. 2:1 is the blend endurance research keeps landing on — a proven default and a low-risk place to start. You don't need to optimize it.
How do carbs help deliver the sodium?: Glucose and sodium cross your gut wall together through the same tiny pump — neither goes through well alone, but paired up they're absorbed quickly, and water follows them in. So the carbohydrate isn't just fuel; it's the ride that carries the sodium and the water into your body. It's the same principle behind medical rehydration drinks.
Why not just take salt tablets and eat sugar separately?: You could, but they do their best work together: the carbohydrate is what helps the sodium and water get absorbed. Putting both in one drink, in the right amounts, is simpler, gentler on your stomach, and means you actually get the teamwork instead of two half-measures.
How much should I take per hour?: Trained athletes commonly target 60–90 g of carbohydrate per hour, which is 1–3 servings of Bonk Juice depending on how long and hard you're going. Your real ceiling depends on how practiced your gut is, so start at the low end and build up gradually rather than maxing out on day one.
How much water do I mix it with?: One serving in 500–750 ml of water. That range keeps the drink close to the concentration of your own blood ('isotonic'), so it leaves your stomach quickly and is comfortable to drink for hours.
Is the citric acid bad for my teeth?: Acids, including the citric acid that gives the drink its tang, can wear at tooth enamel over time — true of any citrusy or sports drink. Rinse with plain water after fueling and avoid brushing immediately afterward. It's a general care note, not a unique downside.

10 · Further reading

The research this is built on

Everything above traces back to published science, not marketing. Here's where to read more.

Glucose-Fructose Hydrogel Enhances Running Performance, Exogenous Carbohydrate Oxidation, and Gastrointestinal ToleranceKing et al., Leeds Beckett University
A Narrative Review of the High-Carbohydrate Fueling Revolution in the Professional PelotonSports Medicine (Springer), 2025
A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During ExerciseJeukendrup, Sports Medicine, 2014
Sodium Intake for Athletes: Review and RecommendationsSports Medicine (Springer), 2025
Compositional Aspects of Beverages Designed to Promote HydrationPMC, 2024
What's Osmolality and Why It Matters for Your Sports DrinkSkratch Labs
Scientific Opinion on Carbohydrate-Electrolyte Solution Health ClaimsEuropean Food Safety Authority (EFSA)
Independent and Combined Effects of Liquid Carbohydrate / Essential Amino Acid Ingestion on Hormonal and Muscular Adaptations Following Resistance Training in Untrained MenBird, Tarpenning & Marino, European Journal of Applied Physiology, 2006
The Effect of Carbohydrate Intake on Muscle Hypertrophy: A Systematic Review and Meta-analysisHenselmans, Vårvik & Izquierdo, Sports Medicine, 2026

Field notes

Plain-language fueling tips drawn from the same research on this page, a few times a year. No spam, no markup.