DIY sports drink

Pick a starting point, then adjust anything. The recipe below is what to weigh out for one bottle, with the osmolality it lands at so you can tell how it will sit in your stomach.

Start from

Light · 4 g/100 ml · 400 mg/l Standard · 6 g/100 ml · 600 mg/l Salty · 6 g/100 ml · 1200 mg/l High-carb · 9 g/100 ml · 900 mg/l

Bottle volume (ml)

Carbs (g per 100 ml)

Sodium (mg per litre)

Drunk over (minutes)

Carbohydrate source

Table sugar only Sucrose is already half glucose, half fructose, and one gram of it adds fewer particles to the drink than a gram of glucose would. Maltodextrin + fructose Lets you pick the glucose-to-fructose ratio and keeps osmolality low, at the cost of buying two powders.

Couldn't calculate

Recipe for one 500 ml bottle

Ingredient	Weigh	Or measure
Table sugar (sucrose)	30 g	2⅜ tbsp

Table salt	0.76 g	⅛ tsp
Water, to make up	500 ml

What that gives you

30 g Carbs in the bottle

300 mg Sodium in the bottle

120 kcal Energy

6% Carb concentration

227 mOsm/l, hypotonic

1 : 1 Glucose : fructose, 15 g / 15 g

If you drink it over the whole session

30 g Carbs per hour

300 mg Sodium per hour

500 ml Fluid per hour

Hypotonic: absorbed faster than plasma, which is what you want when fluid replacement is the priority.

Reading the numbers

Concentration is grams of carbohydrate per 100 ml, which is the same as a percentage. Commercial sports drinks sit around 6%; above roughly 12% most people hit the limit of how fast the stomach empties.

Osmolality estimates how many dissolved particles the drink contains. Blood plasma is about 290 mOsm/l, so anything under 270 counts as hypotonic here and anything over 310 as hypertonic. This is why the sugar you choose matters: one gram of table sugar contributes half as many particles as one gram of glucose, and maltodextrin barely any, so both let you carry more carbohydrate at the same osmolality.

Sodium comes from ordinary table salt, which is 39% sodium by weight — so 1 g of salt carries roughly 393 mg of sodium. Sweat sodium varies enormously between people; 300–600 mg per litre suits most sessions, and 1000 mg or more is for long, hot days or if you are a salty sweater.

Dissolve the powders in a little warm water first, top up, and taste it before you rely on it in a race. A drink you won't finish is worse than a weaker one you will.