# Does cola count as water? Caffeine in a can

A 330 ml cola holds 33 mg of caffeine and 139 calories, and hydrates about as well as plain water. The measurements behind that claim.

## Numbers the app uses

| Field | Value |
| --- | --- |
| Default serving | 330 ml |
| Hydration factor | 1.00 |
| Counts toward the daily goal | 330 ml per serving |
| Caffeine | 33 mg per serving |
| Calories | 42 kcal per 100 ml (139 kcal per serving) |

## The dose is too small to dry you out

A 330 ml can holds 33 mg of caffeine, roughly a tenth of a milligram per
millilitre. Filter coffee runs at about 0.27 mg per millilitre, so cola is
around a third as strong, glass for glass. Caffeine starts producing extra
urine only at far higher doses, and mostly in people who are not used to it.
To get there on cola you would need close to three litres in one sitting.

That is exactly what the controlled trial found. It gave volunteers a litre of
each of thirteen drinks and weighed every urine sample for the next four hours.
Cola and diet cola came out level with still water. The drinks that beat water
were the ones carrying salt and food: oral rehydration solution and milk. So
the app gives cola a hydration factor of 1.00. Drink 330 ml, get 330 ml toward
the goal.

> The beverages that retained more fluid than water were not the ones without
> caffeine. They were the ones with sodium.

## The part worth watching is the sugar

139 calories per can, essentially all of it sugar, is the real cost of the
habit. Three cans a day is over 400 calories that never register as a meal.
This is the one place where the diet version genuinely wins. But note one
detail from the app's catalog: diet soda carries *more* caffeine per serving
than cola does, at 46 mg per 355 ml. That mirrors what is actually in the cans.
Switching to the sugar-free version to sleep better is a plan that quietly
backfires.

## Log the size you actually poured

Cola's caffeine scales with how much you pour. A 500 ml bottle is 50 mg and a
small 200 ml glass is 20 mg. The app files that caffeine into the same
metabolism curve as your coffee, which is the point. An evening cola with
dinner is a small dose, but it lands on top of everything from the afternoon.
The curve shows you the total rather than the individual drinks.

## Source

Hydration factors follow the Beverage Hydration Index. Maughan RJ, Watson P, Cordery PA, et al. “A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index.” American Journal of Clinical Nutrition, 2016;103(3):717-723. https://pubmed.ncbi.nlm.nih.gov/26702122/

Page: https://waterchamp.app/drinks/cola/