Drink Lots of Soup and Broth
Get brothy. Whether you're sick or trying to avoid the flu like the plague, clear broths like miso, chicken or veggie broth, and beef bouillon will keep you hydrated and are easy to digest if you don't have much of an appetite.
Feeling a little hungry? Add chunks of veggies, whole grains like barley, and some kind of lean protein to tack on extra vitamins and nutrients. The hot liquids do double duty by warming the body from chills and also opening up sinus passages to relieve congestion.