Water is an ideal drink to cool your body. If choosing other drinks, when perspiring, consider the caffeine and sugar content. The sugar draws fluids away from the muscles where it's needed, plus adds calories.
You can regain fluids also, by eating these foods: lettuce, pears, tomatoes, corn, apples, oranges, green beans and bananas. Dress in light-weight and light clothing to stay cooler, as this type of clothing reflects the heat and sunlight. If you must be out in extreme heat, wear a hat, sunscreen and let someone know where you'll be and when you'll be home.