A frequent error comes with the use of isotonic drinks when it's not really necessary. They are suitable after intense efforts because otherwise the body restores the balance by itself with a normal diet. A useful reference is running more than ten kilometers, so anyone could compare with other sports. Others say more than one hour of sport.
Anything in relationship with health should be done only after a good research at several sources, specially in Internet. It's true that an isotonic drink doesn't contain toxic elements until a high intake per liter but if the user starts an incorrect diet policy in a reiterative manner it would be easy to experience issues.
Anyway, in case of anyone finds it interesting, there's no mystery in isotonic drinks. Anyone can manufacture at home since the ingredients are common: salt, sodium, potassium and glucose principally.
Here's the recipe from WHO using a liter of water (from Wikipedia):
2.9g potassium chloride (some sea salt comes with potassium)
3.5g sodium chloride (salt)
2.5g sodium bicarbonate (white powder normally available at supermarkets)
20g glucose (sugar)