Children lose water at the same rate as adults. But since they have less body mass, the effects are more severe. When it's hot outside, no heat transfer can occur, and your body overheats like a high-revving car engine. Just 4 to 8 ounces of water can replenish lost fluids. Otherwise, you can get heat cramps or painful muscle spasms.
Water is the best thirst quencher.
Sports drinks and fruit juices are OK, but you have to drink more of them to get a comparable amount of water into your system. Their high-sugar content slows absorption into the body and increases urination, depleting your body's water resources. Soda, coffee and tea have caffeine, a diuretic, which removes fluid from your body. And despite what bleacher bums at baseball games say, the alcohol in beer contributes to dehydration. Their bodies get hot and stay hot.