Battleshots only requires two pizza boxes, a sharpie, and a bunch of shot glasses, all of which are also generally on hand, at least later into the party
We used to do it where we would set up two big squares of cups filled with beer, and the shots were mixed in amongst the cups. So you could see the other side, just didn't know where the shots were. So we were still just throwing balls, but trying to hit the ships. But we also had multiple people on each team because a 30 rack and a fifth for each side is way too much for a single person.