This game is, quite simply, beer pong with special powers. Players take turns bouncing ping pong balls at the opposing goals (cups) that serve as HP. Eliminate the opposing cups first to win.
Players each have a character card granting unique powers, and a deck they customize ahead of time from a large set of options. 10 cards in the deck are special powers and 10 are mana cards that trigger your character's special powers. There are also rules for team variants, and some options to play with a random deck if you don't want to customize a deck for yourself.
The game openly suggests that you play it as a drinking game with alcohol, and players must drink from their HP cups as they are eliminated. One of the character cards has the special power to be the designated driver and never drinks (along with some other special powers too).
Description from the box:
Dungeon Cup is a game that takes the beloved game of Beer Pong and enhances it with a touch of fantasy, roleplaying, strategic card play, team work, and let's not forget, alcohol!
This is a drinking game for 2-4 players. Don't worry though, we have a character for designated drivers too! Seasoned veterans of Beer Pong, Card Game Masters, or Simple Peasants, will all be equals on this battlefield. Some players will win with sheer skills, others a lucky card. Then there are the players with a really high drinking tolerance... So pick a character, and build a deck of cards that suits your play style, or let fate pick your cards for you!