I guess I'd need more details in order to be able to fully form an opinion. (i.e. - were the kids allowed to hydrate throughout practice, and were they throwing up simply from exhaustion? If so, I don't think that's uncommon and isn't necessarily dangerous.) But on the surface, I don't have an issue with this (granted, I recognize it's easy for me to say that when it doesn't involve my own child.)

This is probably going to sound harsh, but if you find yourself taking issue with this method of discipline, I would suggest trying to take a step back to try to re-evaluate things. To a parent it may seem unreasonably harsh, but I believe the coach is trying to teach these young men some valuable lessons that will serve them for the rest of their lives, long after their football days are over. If you don't reinforce what he's trying to do, it's going to have the effect of undermining his authority as coach.

Again, I'm not trying to sound judgmental or preachy. I just agree with others here that coddling kids and insuring that they never encounter hardship/things that are uncomfortable is not the best way to prepare them for becoming independent adults.

As long as the coach isn't truly putting the players' health/safety in danger by not allowing them to take water breaks, I don't think there's any cause for alarm. If you can get behind the coach, I think it will help your son a lot.