Feeding/supplements for sick 8 yr old cat

As you may have seen from a previous post, my cat has tumors/masses on his mesentary lining of the intestines. The outcome doesn't look good and I have chosen to keep him happy at home until I need to make the next move. His appetite seems to be okay as he is eating, just not as much as he used to. I've been enticing him with lamb and turkey baby food which he loves but also encourage him to eat the canned as well. Are there any vitamins or supplements that I can give him to spunk up his appetite more? I know I'm in denial sometimes about his illness but I just want to do all I can for him. Should I try some sort of vitamin or supplement or just continue feeding him as I have been with canned food and baby food? Thank you.