Yellow butter cake buns. Chocolate buttercream hamburger patties with vanilla buttercream lettuce, tomato, and mustard (or cheese). Sorry, I'm not up to date on my SpongeBob trivia!
Speaking of trivia... here's some for ya! From http://en.wikipedia.org/wiki/SpongeBob_SquarePants .
Even though the show is based underwater, the characters can only swim in goo, in Goo Lagoon and in swimming pools. Also, some episodes have featured fires. In "Life of Crime", however, Patrick questions that how can there be a fire if they are under water. The fire then goes out. Also in "Party Pooper Pants", when SpongeBob SquarePants and Patrick get there invitations to the party and the writing is all smudged, they talk about the things that can't occur underwater. So they throw the letters into a fire.