Someone asked how to make a sports drink for after athletics.
The rehydration formula being taught to the third world (to save babies from dying of dehydration) is a pinch of salt, a palm-full of sugar, to half a liter of water.
(If you like, you may add a small sprinkle of potassium, sold as fake table salts such as Nu-Salt next to the regular table salt in the grocery).
I drink the salt, sugar, water mixture whenever I feel dehydrated. The body absorbs this much better than plain water.
Use a search engine to look for "rehydration formula" and you'll find several home versions recommended by World Health Organization, including this simple one and several with more ingredients and more precise measurements.
I once bought a box, about the size tea bags come in, called Electrolyte Stamina, 32 packets of powder you dump in water and claims to have all the major electrolytes. There are undoubtedly other prepared mixes you just add water to. But the home salt/sugar/water formula perks me up. The salt and sugar make the water thinner, drinking a whole glass or more at one time is easy.