Coffee

Coffee cups are a thing found on the reception desk on the first floor of the hotel, near the computers.

Significance
Coffee cups do not affect gameplay. They cannot be interacted with and do not boost the player's speed or anything like that. All throughout the game, none of the maniacs touch the coffee, which probably means that it isn't theirs.

Trivia

 * 1) Given that the coffee is there and hasn't turned black or evaporated, the receptionist workers who the coffee belongs to clearly haven't been gone very long
 * 2) Many players do not even notice the coffee cups, even though it's right in front of them, on the reception desk
 * 3) The coffee cup looks similar to the coffee cup that was reused in The Twins.