Im a 21 year old cancer patient with less than 6 months to live, so ive been in the no-appetite/depression stage many many times.
The drinkable-meal type things are a great help (Boost, Ensure, and similar products) to get enough calories for the day. The best thing to do is mix it with a little ice cream for the added fat and calorie content and blend it into a milkshake. You can drink this slowly over a few hours and its at least 600 calories, plus most of what you need for a non-active lifestyle day.
Other tips are to snack on small things throughout the day, drink soda for the calories/blood sugar so you have enough energy for the basic functions of life. Snacking on small things throughout the day doesnt always work for me. Ill try to force myself to eat, ill get 1-2 bites in before looking at the food makes me feel nauseous. Personally, ive done well with mostly fluids. You dont NEED 2000 calories a day if you are relatively inactive, you can last several weeks without any major ill effects with much much less. About depression, its a personal thing, only you can deal with it. Just try to remember, other people have had it worse than you AND recovered from it. There is always at least SOME hope.