It consists of buns, is very sloppy, and disgusting, as it contains Plankton's Chum, which hardly anyone likes. The things in the chum consists of a band aid, bomb fuse, and duct tape.
Role in the episode
This "Krabby Patty" was made by Plankton in an attempt to make everyone despise Krabby Patties, and to not give their business to the Krusty Krab. When everyone ate it, they got sick and began to hate Krabby Patties. However, SpongeBob sold the real ones, called them new, and everyone liked them again, much to Plankton's dismay and the Krabby Patties became popular again.