I just went on a tour of the Pentagon last week. Here are the food options within the confines of the building:
McDonald’s, Five Guys, Popeye’s, Subway, Panera, Starbucks, Dunkin’, Baskin‑Robbins, Lebanese Taverna, SmokeDatt BBQ, Panda Express, KFC–Pizza Hut–Taco Bell, Sbarro, Moe’s, Jamba, Potbelly, Tropical Smoothie, Fresh Kitchen, Market Basket Café, and Halal Guys.
These were not open when I was on the tour, but there were other 24 hour cafeterias that were serving food.
The Pentagon is incredibly huge and simple to navigate, plus, they get all the cable channels.
Panera is dependable