It looks the same as any other Krabby Patty, but with a bun in place of the meat and it contains no other ingredients. It is said to have stale buns.
Role in episode
As other customers mention the unusual ingredients of their Krabby Patties, Fred says his Krabby Patty is a bun and that the other two buns are still buns and stale. Squidward later mentions that SpongeBob failed his boating exam and that's why he is exhibiting low-effort cooking skills.