Actually I could eat steamed cabbage & often had a small spoonful as my vegetable. I did bring up a slice of well cooked soft carrot (but could eat it in slow cooked soups, mince dishes, etc. - our tummies can be very weird & unpredictable).
Depending upon how soft & fall apart the corned beef is you may be able to eat a small amount of that without the bun. Try a small piece, chew it well & see how you go. You may need some mustard pickles ( without the chunky vegetables) , sauce, etc. to moisten it a bit. Do take your shake, creamed wheat just in case. There’s a lot of trial & error to discover what your tummy will tolerate & it’s ever changing.
Watch the sugar free puddings especially if they are sweetened with artificial sweeteners. They can often upset people & cause diarrhoea, bloating & cramping. And many are extra sensitive to sweet flavours & food can be too sweet.