Thought I'd mention that the United Center in Chicago, where the Bulls and Blackhawks play, has a dedicated gluten free food stand, with Redbridge, hot dogs, nachos and other gluten free snacks. Never has a long line, either. Was awesome going to a Blackhawks game and feeling like a normal person with a hot dog and a beer
U.S. Cellular Field where the White Sox play sells New Grist beer. They also have some gluten free food options, but I don't think there's a dedicated stand for gluten free.