Melrosa,
As Chris mentioned, anything that your husband can get down that has a high calorie count and easy to swallow.
Unfortunately, everything that we eat during our treatments taste like cardboard or aluminiun cans. Hopefully, he hasn't lost the sense of smell. I didn't and it helped a little bit as I would think and remember how it once tasted as I ate different things.
Try mixing up different shakes. I would use some ice cream, a banana, and some instant breakfast mix. Trying to increase the calorie intake and nutrition. I also had a Peg Tube if I couldn't swallow on different days. Each can of nutrition had roughly 275 calories, so I was getting some protien in, etc. Like Chris mentioned, Boost, Ensure, or even the Store Brand. I liked the Strawberry flavor and the Chocolate.
It isn't easy, but he will need to force himself to eat, a task that is much easier said than done when you don't feel yourself.
My Best to You Both and Everyone Here