My Mum has begun to leave most of whatever I give her now but she loves the Kipling apple or apple and blackberry pies so that is what she gets with double cream poured over. She has them every day and never seems to get tired of them. Whilst no-one could say they are healthy, she does, at least, get some calories from them.
I mentioned her lack of appetite to her GP and she prescribed some sachets of powder which, when mixed with milk, give around 300 calories. Mum says they're lovely, and they come in various flavours (I got banana, strawberry and chocolate). The choccy one, I make up with hot milk at bedtime and it goes down a treat.
As I say, not particularly healthy but enough calories to keep Mum from losing too much weight too quickly.