Hmm...there aren't any sushi places that are close to the 9:30 Club. The closest place would probably be Mantis (Columbia Rd.) or Saki (18th & Columbia) in Adams Morgan. It's walkable, but still a distance.
There are a bunch of restaurants on U street and nearby streets, though...Ben's Chili Bowl, Polly's, U-Topia, Local 16, Kuna, St. Ex and a couple of Ethiopian restaurants. Then there are places like Taco Bell/KFC, McDonald's, Subway or 7-11.
Here's a more detailed list.
