They could do like in baseball stadiums and American football stadiums, sellers with chilled trays walking around selling at the seats for beers, sellers with hot dog trays and soft drinks/hot drinks from vending machines OR like we used to do in the Millennium Stadium when i managed the bars there pre-pour beers so its walk up pay & take which saves on long queues waiting for drinks to be poured.
Leave bar empty of furniture and you could get 5 queues leading to bar with one way out and back to seats, much faster.
You can check your sales records for amounts of drinks per game then get an average of each drink. Pre pour for entry, then before end of first period, then again before end of second period and just free pour after game once all pre-pour sold.