I've had a quick look online and they all seem to be flavoured protein shakes that are dairy based and Mum doesn't digest milk well.
Mum is generally very independent but she has a cold/virus that has turned into a chest infection. Anti-biotics and steroids are helping but she WILL NOT eat. She's basically existing on cups of tea, black because she doesn't drink milk.
I know I'm inviting opprobrium from MN by saying anything at all negative about an elderly person, but she is fiercely independent when she is in good health and an oppositional, uncooperative, martyred, pain in the neck when she's ill. So anything that I buy for her to encourage her to eat has to be really tasty because she's not going to push herself to try it just because I am gently encouraging her to. In fact, I might get better results by just leaving some on her kitchen counter-top without mentioning that it's there.
So, is there anything that you have had when recuperating and lacking appetite or that you have bought for an elderly relative/friend that went down well?