Try to get 0.5 oz / pound of body weight of water in to keep you hydrated. Included in those do 2-3 servings of something like Emergen-c or Nuun Sport to get electrolytes in you.
If you are worried about calories go with some calorie dense foods like nuts. I know when I am sick I don't want to eat and know if I want to keep my body mass I need protein so shakes are easy to make into calorie bombs. So some peanut butter with some fruit, oatmeal, protein powder, and MCT oil. Always can sip on those and have each at 500-1000 calories each.