It's mult-factor at this point, with the pain, swelling, lack of saliva, lack of taste, mucocitis, swallowing ability, thrush and other bacterial, viral infections, lack of appetite, energy, and psychological, etc, so it's not one thing that is going to solve all the problems to make one want to or able to eat, plus it takes time. If you try to deal with each one, then maybe eating will improve.

As far as increasing appetite there are presciption meds, and OTC products you can ask the doctor about, foods, like marinol, megace, corticosteroids, steroids, caffeine, wine, sugar, fat, oils, sugar and oil are in most snacks, so you don't stop eating them. Even seeing food can increase appetite, and watching those cooking shows may do it, looking at cooking magazines. Smelling food, but sometimes some may have learned smell aversions from treatment. Some go to a buffet to sample foods to see what is tolerable, tasteful or not instead of eating time and money cooking what one may not eat. There are many other things involved.

Good luck.