Mostly the snack carts. A lot of restaurants like Connections Eatery and Nine Dragons will likely be closed during EEH. If you do want to eat at the sit down restaurants, reserve a spot prior to park closing!
Pretty much everything is closed outside of maybe Connections, and I can't think of anywhere off the top of my head that's still serving at that hour.
But EEH flies by so fast especially at Epcot that you really don't want to waste time doing that anyway even if you could. Everything is spread so far apart you spend most of it walking between rides. My advice is to grab a drink before the fireworks and focus on the rides afterwards. EEH is not wandering and vibing with a drink time and it's not really intended as such.