Hello and thank you for posting. 

You can try and request to speak with the hospital dietician, they can often suggest products. 

Unfortunately, we cannot give you very specific diet advice. If you are having diarrhoea, then reducing high fibre will help, and you can take loperamide capsules to help, and get them prescribed by your GP or hospital team.  

There are some resources that I can signpost you to though,

https://www.macmillan.org.uk/cancer-information-and-support/impacts-of-cancer/building-up-diet/meal-ideas-shopping-list

https://cdn.macmillan.org.uk/dfsmedia/1a6f23537f7f4519bb0cf14c45b2a629/2968-10061/mac13614-e04-building-up-diet-pdf

Sometimes it is possible to able to get a prescription for different drinks through your GP. We have some information on the different types of drinks that you can get here

https://www.cancerresearchuk.org/about-cancer/coping/physically/diet-problems/managing/putting-on-weight/high-calorie-drinks

and more general information about diet issues here, 

https://www.cancerresearchuk.org/about-cancer/coping/physically/diet-problems/types/digestion-problems

The Royal Marsden has produced a cookbook on nutritious food for patients with cancer which you might want to purchase. Have a look here,

https://www.amazon.co.uk/Royal-Marsden-Cancer-Cookbook-Nutritious/dp/0857832328

I hope that this helps,

Best wishes,

Vanda