In Outer Worlds there’s a couple establishments aboard the groundbreaker that could potentially count as fast food by some definition.
The stand on the citadel in mass effect is maybe fast food-ish
I vaguely remember seeing some stands in the background of Babylon 5 that could potentially have been something like fast food, but I never got into Babylon 5 too much so I can’t say much about that, I just have some vague memories of some parts I’ve seen that looked like fast food wouldn’t be out of place.
Pretty much any time there’s a big space station with a city-like interior I assume there’s probably something like fast food somewhere on board, maybe even visible in the background somewhere, though I can’t really think of any particular examples or any time it was specifically highlighted