It's actually an Epic Burger now, I ate there a couple weeks ago. At least the spot near gates 32-34 is an Epic Burger, I think terminal C with gates 40+ may still have a Five Guys
There really isn't much to do at Reagan. It's kind of annoying going back and forth between terminals there and the better shops and restaurants are outside of security. Honestly I would just find a seat and people watch for a bit.