Every June the same advice resurfaces: drink eight glasses of water a day. It's one of those health rules that sounds authoritative and has almost no evidence behind it. For a man sweating through a summer that's already running hot across much of Europe and the US in 2026, the eight-glasses number is both arbitrary and, in some cases, actively counterproductive — because hydration isn't only about water. It's about water plus the salt you lose with it, and getting that balance wrong is how fit, healthy men end up cramping on a Saturday hike or feeling wrecked after a hot round of golf.
Why plain water isn't the whole answer
When you sweat heavily, you lose more than fluid — you lose sodium, and a fair amount of it. Sweat sodium varies a lot between men, but heavy sweaters can shed well over a gram of sodium per litre of sweat, and on a hot day of yard work or a long ride you might lose two or three litres. Drink that loss back with pure water alone and you dilute the sodium that's left, which is the mechanism behind that washed-out, headachy, slightly nauseous feeling after a big sweat. In the extreme — endurance athletes drinking obsessively on a hot day — over-drinking plain water causes hyponatremia, which lands people in hospital every summer.
So the question isn't "am I drinking enough water." It's "am I replacing what I'm actually losing." For most men on a normal day, food handles the sodium and water handles the rest. It's the heavy-sweat days that need a different approach.
When electrolytes actually help
Here's the honest line on the trendy powders. An electrolyte supplement does something real when you're sweating hard for more than about an hour — a long hike, a hot training session, manual work in the sun, the morning after a heavy night out. In those situations replacing sodium alongside fluid genuinely helps you feel and perform better, and the research on sodium and rehydration is solid.
What the marketing won't tell you is that the premium brands are wildly overpriced for what they deliver. The popular packets that run around $1.50 a serving — call them by their colour-coded boxes — are mostly selling you sodium, a little potassium, and flavour at a 1,000% markup. You can replicate the useful part for pennies:
- A quarter-teaspoon of table salt and a squeeze of lemon in a 500ml bottle of water delivers the sodium that matters for a fraction of the cost.
- A glass of milk after a hot session is, oddly, one of the best-studied rehydration drinks there is — the sodium, potassium and protein together beat most sports drinks in head-to-head studies.
- If you want convenience, the cheap generic rehydration salts sold for stomach bugs (oral rehydration solution) are clinically formulated and cost almost nothing. They taste worse than the trendy stuff, but they work better.
The numbers worth knowing
Forget the eight-glasses rule and use thirst plus urine colour, which is what your body actually gives you. Pale-straw urine means you're fine; dark amber means you're behind. On a genuinely hot, active day, a useful target for a man is roughly 500ml of fluid per hour of heavy sweating, with around 300-700mg of sodium per litre once you're past the first hour. That's the entire science, and it fits on a Post-it.
One group should pay closer attention: men on blood pressure medication or with kidney issues, for whom loading up on sodium isn't automatically a good idea. If that's you, the salt-in-the-bottle trick needs a conversation with your doctor first — general advice for a healthy 35-year-old labourer doesn't transfer to a 60-year-old on a low-sodium prescription.
What to actually do this summer
On a normal day, drink to thirst, eat normally, and ignore the powders — your kidneys are extraordinarily good at managing fluid and you don't need to micromanage them. On a hot, sweaty day, add sodium to your fluid, and reach for the cheap option rather than the influencer-endorsed one. And after the big efforts — the long hike, the hot match, the day on the build site — a pint of milk or a generic rehydration sachet will get you right faster and cheaper than the $40 tub gathering condensation in your kitchen.
The whole hydration industry is built on making a simple thing feel complicated so it can sell you a solution. The simple thing is this: replace what you lose, lean on salt when you sweat hard, and don't drown a problem that a quarter-teaspoon would fix.