An on set medic once advised us that when it's really hot weather, or when you're dehydrated, you should alternate water with gatorade, but neither in too much quantity. Gatorade contains a lot of electrolytes and if you drink too much you can actually make it worse. So a nice balance of both is recommended. Also vitamins, like many others have said in other posts. But I always prefer to get my vitamins and minerals from fresh fruits, meats and vegetables. That is of course, once you can keep them down.