If only we had an industrial engineering program to help with efficiencies...
My non-PE suggestions:
1) They should take your order and your $/credit card while you are in line and then will call your name/order # when ready. Takes too long for same person to take your order, take payment and make change, then fill your order while everyone else just waits behind you. Take note of how Disney handles short order concessions.
2) Have someone just filling drinks and placing them in a groove of Cokes, Diet Cokes, Sprites, etc. and they hand one from that when you order, rather than waiting and dispensing the drinks as you order. There would also be the same for popcorn, hot dogs, etc. (like they do the sliding burger rack at McDonald's) so the person filling orders is just grabbing the items on the order receipt and then calling your #.
At a recent basketball game, I watched and there were ~8 people in concession stand with 3 people doing most everything and 5 standing in the back waiting for someone to tell them what to do. It not a shortage of employees, there are just no real systems or efficiencies in place like it's a Starkville 7th grade basketball game concession stand.