The Wash! is a laundromat located in Bikini Bottom. It solely appears in the episode "Mid-Life Crustacean." This is the first place that SpongeBob, Patrick, and Mr. Krabs go on their night out followed by many other places. It is implied that SpongeBob and Patrick visit often. It is also revealed that SpongeBob and Patrick enjoy watching clothes spin around in a washing machine. Interestingly enough, another laundromat appears in the episode "Shuffleboarding," but they are not the same place.
In The Yellow Avenger, it appears in the intro when SpongeBob and Mermaid Man go there to free Barnacle Boy
In Reef Rumble, the inside appears if you fight against Squidward.
If you look closely inside, there is poster saying "Lost" with a picture of underwear and socks.