Hot hot hot! Hydrate hydrate hydrate!

[Paul Nevins]

http://bicycletimesmag.com/how-to-stay-hydrated-in-the-heat/
As Robert advised keep plenty of electrolytes in your drink.
My personal recipe is coconut water with a teaspoon of sea salt and a teaspoon of coconut sugar. Dried figs have more electrolytes than bananas and good carbs too.