Revealing mistake: When Jesse is cleaning out his room, he puts a tape into his tape player, and presses a button down on the top of it. But halfway though the scene of him packing his things away, you can clearly see the button is no longer pressed down, yet the tape still plays. (00:18:10 - 00:19:00)
Revealing mistake: When the crazy bird is let out of the cage it starts flying around. Then it explodes in mid-air. A split-second before it explodes you can clearly see the size of the bird increase by about three times. (00:28:15)
Revealing mistake: When Jesse and Lisa are reading the diary you see the pages in the diary are clean. Nothing is written in the pages they are reading from. (00:21:35)
Revealing mistake: When the tennis balls pop out of the tubes at Schneider, you can clearly see a hole cut into the bottom of each tennis tube. (00:33:15)
Revealing mistake: When the sausages catch fire at the party, you can see the flammable liquid surrounding and covering them. (01:00:45)
Revealing mistake: At the end of the film, Jesse and Lisa react way too early to Freddy bursting out of the girl sitting behind them. (01:18:52)
Revealing mistake: Freddy bites Lisa on the leg. When she starts to kick him, you can see it's Lisa's stunt double.
Revealing mistake: When the bird is flying around acting crazy, both lamps get knocked off the tables, yet the room stays lit up.
Revealing mistake: When the iron poles catch fire you can see the fluid which burns. (01:14:35)
Revealing mistake: When Freddy pulls open his head, revealing his brain right before he pulls his skin back, you can see his eyelashes in one shot with a close-up of his face.
Revealing mistake: When Freddy bursts out of the ground at the pool party look closely. The facial makeup's different looking. Clearly this a stuntman.
Answer: I think the coach's death was a play on his character being at a S&M bar. People who frequent those places are usually into bondage and being dominated. Hence being tied up, and whipped with the towel. It also fits in with the homoerotic subtext throughout the movie.