Cup is a multiplayer type of Race mode.
Each player is awarded a certain amount of points depending on which position they take in a race, and they will continue to race until there are three winners. At some point, the players will meet a maximum point limit and become finalists. The first three finalists to each take the first position at some point will be the three winners.
This mode is similar to Rounds, except that the courses change more frequently in Rounds in comparison to Cup.