The ghost of soda drink hats is a paper ghost who only appears in the episode "One Krabs Trash."
It is actually Mr. Krabs with a fishing rod holding a poorly drawn picture of a ghost with a shopping list on the other side. Mr. Krabs shakes and waves the paper to make it look like the ghost is moving. Despite its fakeness, SpongeBob never notices it is a trick by Mr. Krabs.
The ghost is another scheme Mr. Krabs used to try and get SpongeBob to give him his soda drinking hat back. Mr. Krabs attaches the paper ghost onto a fishing rod and hangs it inside SpongeBob's bedroom window for him to see. SpongeBob thinks he is a floating shopping list at first because the paper is turned the opposite way.
After turning the paper, he tells SpongeBob that the hat he possessed was cursed. He told him he had to return it to its original owner, Smitty Werben Jagerman Jensen, who was "number one in Bogeyland," or the hat will curse him. When SpongeBob asks if he should really give it immediately, the ghost shakes up and down, yelling.