how much water do they drink?
They only drink when they are thirsty. No more than that.
I do agree that they need to have a workout partner. My oldest son would run with his best friend early in the morning and sometimes in the evenings. Having a friend run with you makes you more committeed than trying to do it on your own. Each pushes the other.
When my oldest son was in junior high, he didn't like to just run so instead, he would get a few of his friends together and they would all play pick-up basketball. He was still running but at the same time, he was with his friends enjoying another sport.