Fiber
Fiber, or dietary fiber to be specific, is a material in foods which aids the digestive system in digesting materials.
Summary of role
It was seen in Mermaid Man vs. SpongeBob when SpongeBob tried to end Plankton's mind control over Mermaid Man and Barnacle Boy. SpongeBob managed to get the controlled minions to consume the Krabby Patties, but the two weren't able to digest it until SpongeBob brought a concrete mixer filled with fiber and fed the fiber to them, making them snap out of mind control.
In "Penny Foolish," Mr. Krabs was at his favorite market, Discount Grocery Mart, and one of the items he bought was raw fiber.