There are several options for staying hydrated on extremely hot days .
Hopefully, you've been sipping plain old-fashioned water throughout the day - especially if you've had to spend any part of it outside. Most doctors agree that unless you're spending prolonged amounts of time outdoors, you don't have to pay extra for a fancy sports drink. But, if you work or exercise outside in hot weather for big parts of the day, sports drinks can help because they replace lost electrolytes and keep your blood sugar levels stable.
If you're really concerned about putting back what gets lost when you sweat a lot, some doctors say coconut water fills the bill. It's got more potassium than a banana and more electrolytes than sports drinks. In fact, doctors have used coconut water as emergency IV fluid when nothing else was available.
Just be sure to avoid alcoholic and caffeinated drinks because although they may seem refreshing, they'll actually make you more dehydrated in the long run.