It is a sloppy chumburger that consists of buns and is meant to be disgusting, as it contains chum. The ingredients in the chum consist of a band-aid, a bomb fuse, and glass.
Role in episode
This "Krabby Patty" is made by Plankton in an attempt to make everyone despise the real Krabby Patties and not give their business to the Krusty Krab. When everyone eats it, they get sick and begin to hate Krabby Patties. However, SpongeBob sells the real ones, calls them new, and everyone likes them again, much to Plankton's dismay.