Hi Jack,
There's lots of reasons why one could suddenly vomit in this early stage of post Tx. Radiation sickness, phlegm "stuck" in the back of the throat or thick mucous, constipation, messed up nerve endings from radiation burns, thrush, ongoing toxicity from the chemo, etc. It's almost impossible to clear your throat in the normal way this early on. I had to experiment a lot to find techniques to get food down and keep it there. And even so, I still vomited a fair amount up to a month ot two post Tx. I would vomit routinely after the lidocaine (pink magic)swish & spit. It still worked though.
I did ok with eggs, scrambled. Like Mark, meat was the very first thing I tried and it was very rare (still mooing) filet mignon and it was delicious. Tip: it HAS to be moist. I had to take my time and eat small bites and ofentimes it would get stuck in my throat. It is an art to swallow the right amount of liquids to flush it done since the swallowing muscles are damaged and not fully functional, add to that zerostomia and it can creats some predictable difficulties.