In the scene, someone called Mental is holding Harry and Lloyd hostage. They stop to get something to eat, and Harry and Lloyd try a prank which brings about an allergic reaction. They then try to rescue Mental with “CPR.” Or at least their own variation of it.
It starts with Mental having each of the others try these hot peppers. He leaves to make a phone call, and by the time he comes back, the guys have put the peppers on his burger. He has an allergic reaction to the peppers and falls onto the floor. Harry and Lloyd react quickly, pumping his legs in a ridiculous “heimlich” maneuver that isn’t, and then beating him on the chest. One of them tries to give rescue breaths, which Mental stops from happening. Mental does, however, carry pills with him, but he’s left those in the van. Instead, he had rat poison, which he’d intended on using on Harry and Lloyd. They give him the poison, thinking it’s the pills that he needs, and he finally passes out.
Watch the Video (Warning, some strong language. May not be safe for work.)