Pumpkin Juice

Pumpkin juice, which is usually served iced, available on the Hogwarts Express and at Hogwarts (GF12, GF31).

• While flying to Hogwarts in the flying Ford Anglia with Ron, Harry ate too much toffee and began to fantasize about drinking "ice-cold pumpkin juice" from the Hogwarts Express trolley. When they crashed the car into the Whomping Willow, McGonagall made sandwiches and pumpkin juice appear on Snape's desk (CS5)
• Snape threatened to put some Veritaserum in Harry's evening pumpkin juice to get the truth when he thought the Gryffindors were stealing Polyjuice Potion ingredients as they had done the year before. This time, it was Fake-Moody, getting ingredients to keep his identity a secret (GF27).  This explained why Moody had ignored his flagon of pumpkin juice at the first-night feast and drank from a flask instead -- he wasn't just afraid of being poisoned, but needed to keep drinking the potion (GF12)
• Hermione spilled her pumpkin juice when she found out there were over 100 house-elves living and working Hogwarts, yet she hadn't seen one (GF12).
• Harry pretended to put the potion Felix Felicis into Ron's pumpkin juice at breakfast to give him confidence for a Quidditch match with Slytherin in sixth year, and it worked (HBP14).

A Scouring Charm can remove pumpkin juice stains. (BoS)