Does Soda Count Toward Your Water Intake?

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You skip soda because it feels like the opposite of hydration: all sugar and fizz, nothing like a glass of water. The research says otherwise. A randomized hydration trial found cola and diet cola perform no differently than plain water. Soda counts toward your fluid total, it just doesn’t come free.

Where the “soda doesn’t hydrate” idea began

Soda earned its reputation the same way sugar did: guilt by association. Decades of nutrition advice warned against sugary drinks, and somewhere along the way “watch the sugar” turned into “it doesn’t hydrate you.” Those are two different claims. One is about your fluid balance. The other is about your diet. A can of soda is roughly 90% water, and that water still counts once it’s in you.

What’s actually in a can of soda

Strip out the fizz and a can of regular soda is mostly water carrying two extras:

• Sugar. Brim’s own nutrition data puts a 330 ml can, the app’s default soda serving, at roughly 35 g of sugar, about 8 teaspoons.
• Caffeine, in colas only. A cola-style soda carries a small dose, well under a cup of coffee. Clear lemon-lime and root beer sodas carry none.

A single can of regular soda can blow past a woman’s entire daily added-sugar allowance, and it is still mostly water underneath that sugar.

Neither extra fights the water already in the can. Sugar doesn’t pull fluid out of you at everyday soda doses, and the caffeine in a cola sits far below the roughly 250–300 mg single dose that reviews (Maughan & Griffin, 2003) tie to any measurable diuretic effect.

Why soda still counts as hydration

The best test of soda’s hydrating power came from the same trial that put coffee, tea and milk head-to-head against water. Maughan and colleagues (2016) gave healthy adults a liter of water plus one of thirteen test drinks, then tracked how much came back out as urine over the next four hours. Water set the 1.00 benchmark. Milk and an oral rehydration solution scored higher, their protein and electrolytes hold fluid in longer. Cola and diet cola landed right on water’s line, no significant difference either way.

That result holds regardless of the sugar. A sugar-free cola and a fully sugared one hydrated people the same. Whatever else is riding along in the can, the water in it still does its job.

How to count soda toward hydration

So should a tracker score a can of soda the same as a glass of water? Our honest answer: not quite, and not because of the fluid.

We built Brim to log soda’s water content while nudging you toward drinks that don’t carry a can’s worth of sugar along with it. A can of soda credits at 80% of water (Premium), a shade below the lab number. That’s not a lab figure like the BHI panel above, it’s a deliberate nudge, the same conservative logic we apply to coffee and milk elsewhere: cautious beats clever where the real cost is sugar, not water.

Curious exactly how much sugar you’re logging along with the fluid? The Sugar in Drinks tool breaks a can down by teaspoon, next to juice and sports drinks.

How much soda is too much?

The ceiling that matters for soda was never hydration. It’s sugar. The American Heart Association caps added sugar at about 6 teaspoons (25 g) a day for women and 9 teaspoons (36 g) for men, from every source combined, not just drinks. One regular can is enough to spend that whole budget in a single sitting.

Caffeine is the smaller concern. A can of cola carries a fraction of a cup of coffee’s dose, well under the 250–300 mg threshold reviews tie to any diuretic effect.

Does diet soda change the answer?

Diet soda removes the sugar question and leaves the hydration answer untouched. In the same trial, diet cola scored no differently from water, same as the sugared version. If fluid is your only goal, the two are interchangeable.

What’s left to weigh is everything that trial didn’t measure: taste, artificial sweeteners, whatever your own gut tells you about how much soda belongs in a day. None of that changes the fluid math. Diet or regular, a cola hydrates the same; the only difference is the sugar, not the water.

Key takeaways