There are not set rules to beer pong. Meaning that the number of cups, how full the cups are and the number of players on each team varies from game to game. Create a shirt that lists your house rules. Then when you go to play, wear the shirt so people know exactly how the game is to be played. For example, designate no more than four players per team, each cup is filled with 3 oz. of beer and there are no double bounce shots. Create the shirt using the rules you play with on a regular basis. You can even create a special house rule on the shirt. For example, state clearly that your team always go first.
As you play beer pong more and more, you might find a core group of players that make-up your team. Give yourselves a team name, colors and even a logo. Add a team slogan meant to intimidate the other team. For example, if your team is named the Wizards, create a slogan that reads "You are under our spell!" Then order shirts from a custom shirt company and wear them when you play. Consider personalizing the shirts with each person's name and the order which they play in the game.
Part of the art of beer pong is the many different shots you can perfect in order to sink your ping pong ball in the other team's cup. Create a shirt that shows a diagram of each shot along with name. For example, a high arcing shot might be called the "floater," a bounce shot might be called the "bouncer," a shot on a straight line might be referred to as a "line drive." Be creative with the shots and the names for your shirt. Then submit your artwork to a custom shirt design company and place your order.
Use a famous or branded image, except alter it into a beer pong shirt. For example, the infamous Uncle Sam army image saying "We Want You" can be altered into a shirt that states "We Want You For Our Beer Pong Team." Or take a professional sports image such as the PBA symbol or NBA symbol and alter it to show an image of a beer pong player in mid-toss along with a slogan such as "I Went Pro." Use your imagination and borrow and alter images that are in the zeitgeist and make them into a beer pong shirt. Then, place an order with a custom shirt store.