Teaism ($$) has become one of my regular stops in D.C. since I've moved here. There are three locations, conveniently all within 20 minutes from my dorm in Dupont Circle, Chinatown, and Penn Quarter (Note to tourists: the Penn Quarter location is close to all of the Smithsonian Museums so it is a convenient spot if you plan on going). Teaism is an Asian tea house, with full sized meals as well as smaller snack items. It is a great place to study or hang out for hours with a book because they have free refills which gives you a reason to be there for an extended period of time!
Thai Chicken Curry (which is very spicy so make sure to grab at least two extra glasses of water when drinking), the Curried Chicken Salad, and the Salmon Bento Box which comes with brown rice, edamame, and a cucumber-ginger salad. They also have desserts such as Coconut Rice Pudding, Ginger Scones, and their famous Salty Oat Cookies. Okay, I know salt on a cookie may not sound that appealing- but there is a reason these cookies are their signature item. Now of course- the tea. Their Japanese Sweet Green Tea is my favorite, and the Assam Black Tea is a solid option. Their Ginger Limeade and Chai Shake are also great refreshing drinks.