Hello Wendy. I would be curious to know what anti-nausea meds he's tried. I saw Zofran mentioned. And I saw that ice chips/ginger/CBD were also suggested but none of that worked for me. Here's what did:

Zofran (ondansetron) 8 mg three times a day for 3 days starting day of treatment
Decadron 4 mg twice a day for 3 days starting day of treatment (taken with food)
Compazine 10 mg (prochlorperazine) every 6 hours as needed

I was asked to stop Decadron after 3 days but to continue with Zofran and Compazine as needed. And it was. I also tried cannabis (not CBD but THC) and it was helpful in providing me with a good nights sleep. Later, four or five days after a cycle when things started to settle, it sometimes stimulated my appetite- that's when I would lean on anything I could get down and really try and pack in those calories. If he can swallow then bring on the milkshakes.

I was also given a shot for nausea which I don't remember the name of- it was in a little box that was taped to my upper arm. It was on a timer and went off 24hrs after my cycle. I can find out the name of it if you want. I was still in a flop sweat half the time, clammy and uncomfortable, dizzy and tired and without any appetite. But I didn't throw up. It wasn't easy but it helped. I'm sorry he's having to go through all this again. Hang in there.