Not a nutritionist..but try some Ensure Plus. High in calories, but nutrients too!! Its best really cold, but not bad at room temp, kind of like a milkshake! Its made by Abbott Nutrition (same people that make Similac). Its a little pricey, but you can probably find coupons somewhere. We gave it to my mom when she was on chemo and didn't want to eat. They have lots of flavors. I think they also make one with fiber if you want it. They have an online store, or you can get it at the grocery and drug store, although their flavor selection may be limited.