Why do NFL players throw water on their coach after they win the Super Bowl?

I believe the answer is: They don't. They dump Gatorade.

Tradition. Same way that NASCAR winners drink milk at the end of the race. Could also be a way of "getting even" for having their coach yell at them during the game :)

Drivers drink milk at the Indy 500, not Nascar

The "Gatorade Shower."

"The Gatorade shower, also known as the Gatorade dunk and the Gatorade bath, is a sports tradition involving dumping a cooler full of liquid (most commonly Gatorade) over a coach's (or occasionally star player or owner's) head following a meaningful win. The tradition began with the New York Giants football team in the mid-80s. According to several sources, including Jim Burt of the Giants, it began on October 28th, 1985, when Burt performed the action on Bill Parcells after being angered over the coach's treatment of him that week.[1]. However, former Bears defensive tackle Dan Hampton claims he invented the shower in 1984 when the Bears dunked Mike Ditka upon clinching the NFL Central.[1] The phenomenon gained national attention in the 1986 Giant's season. Parcells would be doused after 17 victories that season, culminating with Super Bowl XXI."

If I recall correctly, it was the Giants and Parcells that began this tradition.

https://en.wikipedia.org/wiki/Gatorade_Shower

More often than not, it is water. Water is the most common sideline drink.

thank you for the answer my 6 yr old son wanted to know and i didnt have the answer because im not into football like that and he is so thank you very much

They use a huge Gatorade container, but it must be water because Gatorade would be very sticky if it was poured all over a person.