Hi, I'm going through chemo at the moment so will give you some ideas based on what I have found useful.
Friends have been amazingly kind with gifts.
Home made veggie soup and bread for the freezer is a great idea. A water bottle or healthy (ish) snacks. Hand cream and lip balm both good too.
I am finding being at home not doing much quite difficult/boring. Depending on his interests, a subscription to TV (eg Disney), Duolingo, online learning like Masterclass or BBC Maestro, or online theatre like National Theatre could work too. Or vouchers for something like Class Bento so he can find some new activities locally or online.
The charity Mind have a subscription box with mindfulness gifts. Other subscription boxes could be an option - targeted to their interests - eg an online book club.
Each different type of chemo will have slightly different side effects so if you're able to Google the type of cancer or type of chemo and look up the likely side effects that would help you target things more.
For example, my chemo (Capox) means very cold hands and feet so thick socks and gloves are particularly useful. Comfy blanket and v shaped pillow have been useful. Vicks First Defense, disposable face masks and hand sanitisers all helpful too.
Hopefully something of use here. Even just a little thing from a friend means a lot. Whenever I pick up a little something a friend has given me, it makes me smile. Feeling supported and thought of through a difficult time is priceless.