Milk
Milk is a drink that appears in some games. In Paper Mario, it is one of the items Princess Peach uses to bake a cake for Gourmet Guy. It also makes a very brief appearance in Mario & Luigi: Partners in Time, when up in Yoshi's Island Mountain Top, Kamek gives milk from an "evil" cow to Baby Bowser, who chokes while eating Yoshi Cookies. Milk was also referenced in Super Paper Mario, where a non-player character named Chap showed a bit of an obsession with it and often claimed to be drinking it (despite the fact that it was never seen) when spoken to in the Underwhere Bar. In Mario Kart Wii, milk is advertised in signs of Moo Moo Meadows, and bottles of milk can be seen throughout the course.
Its item description: Milk, fresh from the cow!
Milk also appeared in an old commercial featuring Mario, where a few children were playing Super Mario 64; however, Mario wasn't jumping high enough. The kids left frustrated. Mario then jumped out of the TV, ran through the house, made it into the family's refrigerator and drank a whole bottle of milk. Mario then returned to the TV and was now bigger and stronger. This advertisement was part of the "Got Milk?" commercials, and also had a printed correspondent, in which a milk-powered Mario grew so large that he destroyed the television his game was being played on.