Everybody needs water!
When it's hot outside and you've been sweating, you get thirsty. Why? Thirst is a sign of dehydration. Dehydration means that your body doesn't have enough water in it to keep it working right. A person gets water by drinking and eating. You lose water when you sweat, urinate, have diarrhea, or throw up. You even lose a little water when you breathe.

Our bodies need water to work properly. Usually, you can make up for the water you lose — like when you come in from outside and have a long, cool drink of water. If you don't replace the water your body has lost, you might start feeling sick. And if you go too long without the water you need, you can become very ill and might need to go to the hospital.

Many times kids get dehydrated when they are playing hard and having fun. Have you ever gotten really sweaty and red-faced when you've been playing? This often happens when it's hot outside, but it can happen indoors, too, like if you're practicing basketball in a gym.

Kids also can get dehydrated when they're sick. If you have a stomach virus, you might throw up or have diarrhea. On top of that, you probably don't feel very much like eating or drinking. If you have a sore throat, you might find it hard to swallow food or drink. And if you have a fever, you can lose fluids because water evaporates from your skin in an attempt to cool your body down. That's why your mom or dad tells you to drink a lot of fluids when you're sick.

In addition to being thirsty, other signs of dehydration are feeling lightheaded, dizzy, or tired, having a rapid heartbeat, or dry lips and mouth.

If you can, try not to get dehydrated in the first place. If you're going to be going outside, it's a good idea to drink water before, during, and after you play, especially if it's hot. Dehydration can happen along with heat-related illnesses, such as heat exhaustion and heat stroke. In addition to drinking water, it's smart to dress in cool clothes and take breaks indoors or at least in the shade.

If you're sick, keep taking small sips of drinks and soups, even if you're not that thirsty or hungry. Eating an icepop is a great way to get fluids. How is an icepop a liquid? Well, it's basically frozen water and flavoring. The warmth in your mouth and stomach turns it from a solid to a liquid. Other foods, such as fruits and vegetables, contain water, too.

So do you have to drink eight glasses of water a day? No, but you do need to drink enough to satisfy your thirst, and maybe a little extra if you're sick or if you're going to be exercising. The best drink is water, of course, but milk is another great drink for kids. Juice is OK, but choose it less often than water and milk. Sports drinks are fine once in a while, but water should be considered the drink of champions.

Limit soda and other sugary drinks, such as fruit punches, lemonades, and iced teas. These drinks contain a lot of sugar that your body doesn't need. Some of them also contain caffeine, which is a diuretic. This means that caffeinated drinks cause you to urinate more often than normal. In other words, they tell your body to get rid of fluids. And as you now know, that's the opposite of what you need to do if you're dehydrated!
http://www.kidshealth.org/kid/watch/er/dehydration.html