In most episodes, it is designed as a casual sink with a faucet and also is shown to have a disposal in the sink. In "New Digs," it is designed as a conveyor-belt wash.
Role in series
The dishwasher appears at the beginning of the episode when SpongeBob uses it during his night shift. As his surroundings start to spook him, he washes all of the dishes in the quickest amount of time possible and tells Mr. Krabs he will be leaving.
SpongeBob uses the dishwasher conveyer belt in the kitchen as a bathtub to clean the ketchup and mustard stains off of his shirt. Squidward enters the kitchen, holding a bucket of dishes to insert into the dishwasher, but then realizes it is jammed. He reaches into the machine to retrieve the dishes clogging it, only for SpongeBob to be bathing in there.
"The Krusty Plate"
At the beginning of the episode, SpongeBob uses the dishwasher during his night shift. Once he cleans the last dish, he proceeds to get off work, only for Mr. Krabs to point out the missed spot on one of the plates, demanding SpongeBob not to leave the restaurant until the spot is removed.
Unfortunately for SpongeBob, the spot on the plate takes more than just the dishwasher to be cleaned.
After Mr. Krabs thinks SpongeBob knows his secret about his split nail, he washes dishes and breaks said nail.
"Gramma's Secret Recipe"
Plankton ties up a balloon that looks like him dressing up as SpongeBob's great grandmother. It flies away into the dishwasher, and when SpongeBob turns it on, the balloon pops. SpongeBob, thinking it is his great grandma, cries, but then Plankton re-appears.