Soda vs Water: Hydration Comparison
Which is better for staying hydrated?
Quick answer
Soda vs Water: Hydration Comparison
Surprisingly, soda hydrates you. In the Beverage Hydration Index (Maughan 2016), 1 L of cola produced 4-hour urine output no different from water, and a cola's ~22–37 mg of caffeine sits far below the ~250–300 mg diuretic threshold. So soda isn't dehydrating — but its sugar still makes water the smarter all-day choice.
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While soda is technically a liquid and does contain water, it's one of the worst choices for hydration. The combination of high sugar (or artificial sweeteners), caffeine, phosphoric acid, and carbonation makes it counterproductive for staying hydrated. Regular soda consumption is linked to obesity, type 2 diabetes, tooth decay, and bone density loss. Water wins this comparison decisively.
Key Differences
Sugar Content
A 12oz can of regular soda contains 39g of sugar (about 10 teaspoons). This excess sugar can actually increase thirst and fluid needs. Water has zero sugar.
Health Impact
Regular soda consumption is associated with weight gain, diabetes, heart disease, and tooth decay. Water has only positive health effects.
Caffeine Effect
Most colas contain 30-50mg of caffeine, which has a mild diuretic effect. Combined with sugar, this reduces net hydration compared to water.
Acid Content
Soda contains phosphoric and citric acids (pH 2.5-3.5) that erode tooth enamel. Water is neutral and protects dental health.
Head-to-Head Comparison
| Feature | Soda | Water |
|---|---|---|
| Hydration Factor | Poor | Excellent |
| Calories | 140 per 12oz | 0 |
| Cost | $1-2 per can | Near free (tap) |
| Convenience | Purchase required | Always available |
| Taste | Sweet, carbonated | Neutral |
| Best For | Occasional treat only | All-day hydration |
Which Should You Choose?
- Water is the clear winner for hydration — there's no scenario where soda is a better hydration choice.
- If you crave fizz, switch to sparkling water with a splash of fruit for a healthier alternative.
- Gradually reduce soda intake rather than quitting cold turkey for more sustainable change.
- Each soda you replace with water saves 140+ calories and 39g of sugar.
- Use Vari to track your transition from soda to water and watch your hydration improve.
Medical Disclaimer: This comparison is for informational purposes. Individual hydration needs vary.
Sources & Citations
- BHI ≈ 1.0 (no significant difference vs water) — At 1 L, cola and diet cola produced 4-hour urine output not significantly different from water (BHI ≈ 1.0), so cola is not net-dehydrating at this dose.[1]
- 0 beverages below water (n.s.) — No beverage tested — including cola, tea, coffee and lager — had a hydration index significantly below water; none caused net dehydration at 1 L.[1]
- ≥250–300 mg acute threshold — Caffeine produces a diuretic effect only at large acute doses of at least 250–300 mg; standard servings of soft drinks have no diuretic action.[2]
- 400 mg/day; 200 mg single dose — EFSA judges habitual caffeine intake up to 400 mg/day, and single doses up to 200 mg, safe for healthy non-pregnant adults — well above a cola's ~22–37 mg per can.[3]
- [1]Maughan 2016 (Beverage Hydration Index) — Maughan RJ, Watson P, Cordery PA, Walsh NP, Oliver SJ, Dolci A, Rodriguez-Sanchez N, Galloway SD. A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index. Am J Clin Nutr. 2016 Mar;103(3):717–23.PMID: 26702122DOI: 10.3945/ajcn.115.114769
- [2]Maughan & Griffin 2003 (Caffeine & fluid balance) — Maughan RJ, Griffin J. Caffeine ingestion and fluid balance: a review. Journal of Human Nutrition and Dietetics. 2003 Dec;16(6):411–420.PMID: 19774754DOI: 10.1046/j.1365-277X.2003.00477.x
- [3]EFSA 2015 (Caffeine safety opinion) — EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on the safety of caffeine. EFSA Journal. 2015;13(5):4102.DOI: 10.2903/j.efsa.2015.4102
Last reviewed: 2026-06-21. Every figure on this page is sourced to the named primary references above.
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Frequently Asked Questions
Does soda count as water intake?
While soda contains water, its sugar and caffeine reduce its hydration effectiveness. It's better to not count soda toward your daily water goal and instead track it separately.
Is diet soda better for hydration?
Diet soda eliminates the sugar issue and hydrates somewhat better than regular soda. However, artificial sweeteners may still increase thirst in some people. Water remains superior.
How much sugar is in soda?
A 12oz can of regular cola contains about 39g (10 teaspoons) of sugar. A 20oz bottle has 65g. The WHO recommends no more than 25g of added sugar per day.
Can soda cause dehydration?
While a single soda won't dehydrate you, regular consumption and the sugar/caffeine content can impair optimal hydration. Replacing soda with water measurably improves hydration status.
What's the best way to quit soda?
Try sparkling water with fruit, gradually reduce intake, and track your water consumption. Many people find that after 2-3 weeks without soda, they no longer crave it.
How many calories would I save by switching to water?
If you drink 2 sodas per day, switching to water saves about 280 calories daily, or roughly 29 pounds worth of calories per year.
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