Sports drinks certainly help if you are sweating moderately, but are inadequate for intense exercise in the heat. When you are sweating intensely (>1L/h of sweat), you can lose sodium at over 1000mg/L. Supplementing sodium and other electrolytes may be necessary.
As a comparison, for oral hydration, WHO/UNICEF has 13.5 g/L of glucose and 2.6 g/L of salt (NaCL) in their formula:
* https://en.wikipedia.org/wiki/Oral_rehydration_therapy
That's about 6 teaspoons of sugar and half a teaspoon of salt if all you have is volumetric measures.
For serious, medical dehydration use commercially-available oral rehydration salts: a homemade brew may not be enough (e.g., the packaged stuff also has potassium).
[1] https://www.gastrojournal.org/article/S0016-5085(97)70034-9/...
It is best to simply drink enough tap water with a meal. This will naturally balance the salt. If you are really concerned about your salt balance outside of meal hours, the article recommends you drink your tap water with a little snack like a banana, or drink milk or coconut water instead.
I've myself also used bottled spring water naturally high in minerals (mineral water). I find this water the best heat wave drink, but some brands are ruined by adding sugar or other sweeteners.
Does anyone know a recipe or brand that tastes good?
I've tried different brands, and it all tasted too unpleasant to drink for me, though I didn't have a critical need for it.
I also made it at home [1], and tried adding some lemon juice to that recipe. The taste resembled a sports drink, but again wasn't sufficient to drink daily.
[1] 1 liter water, 8 tsp sugar, 1 tsp salt https://www.britannica.com/science/oral-rehydration-therapy
Pocari is still very sweet and tends to upset my stomach a bit if I drink more than a cup or so.
anyway i prefer boss coffee. the boss of all bosses. or bickle.
[edit: changed "killed himself with" to "died of"; the man wasn't suicidal]
Never did find out what sort of animal a Pocari is, or how they collected its sweat.
Never seen it in Australia (Victoria), but could imagine it would be in smaller speciality grocers in some regions.
https://en.wikipedia.org/wiki/Pocari_Sweat
It's a soft drink specifically designed to avoid you getting hyponatremia, and was apparently inspired by doctors who would drink the contents of saline IV pouches.
Like many asian soft drinks it's not very sweet but it's not unpleasant. If you live on the US west coast you can find it in most Japanese supermarkets.