Don't be surprised if your mum really doesn't want to eat much during treatment. I lived on custard, weetbix and Yakult pretty much but I could afford to lose a few kgs and it wasn't too much of an issue. I had that heartburn really bad and the meds I think were almost as bad as the complaint. I learned to eat a whole lot less and just have a little bit of food more often. Re the water, I had and still have a drink bottle of water and while I don't drink quite as much any more, I do still sip it all day and night. Little and often is the key and if your mums losing too much weight then get on to the Up and Go drinks. My dad is on those and its often all he can tolerate during chemo. He sometimes drinks up to 8 of them a day and that's all apart from an occasional cuppa.