I just returned home after a 4-day stay at the hospital for major (but successful!) surgery (yay me!) I couldn't eat anything the first day, and the second day they started me on a liquid diet. I got chicken broth, jell-o, and apple juice.

When the nurse came by, I reminded her that I'd written "vegan" on my application. She said "Oh, sorry." When my evening tray came, I got...beef broth, jell-o, and apple juice (did I mention I hate apple juice?). When I saw the (new) nurse I told her that I was vegan, and she suggested I have my husband bring me food from home!
The next morning my doctor came by to see me and I told her about the food. She promised to get me something to eat, as I was starting solid foods that day. I got a liquid tray that morning with juice, a popsicle (!!) and vegetable broth (so good).
That afternoon I got another liquids tray (no popsicle!) and I was ready to raise a fuss when a second tray was delivered. "Sorry, we just noticed you were on solid foods now." It was AMAZING! I had: a bun, some margarine, a green salad (well...iceberg lettuce and carrots, and a little purple cabbage, better than nothing) with balsalmic vinagrette, green beans, rice, and "sweet and sour tofu" which tasted fantastic. I wasn't sure about the bun and margarine, but I decided to pick my battles.
The breakfast tray was whole-wheat toast with peanut butter, coffee with packets of sugar and non-dairy creamer, hot water and teabags, juice (oj this time, I think) and a popsicle (!!!). I took a look at the non-dairy creamer out of curiosity, since I know they're often not vegan, but this one actually had no dairy at all. So maybe the bun and marg were okay. I don't use creamer anyway (and hadn't the stomach for coffee).
My last tray before I left was "vegan jambalaya" (basically tofu cubes with mixed vegetables and rice) and the salad (italian dressing this time) and the bun, and it was great. So although I had trouble convincing the staff I really
was vegan, I wound up eating well by the time I left. And I thanked my doctor profusely. Also, I love popsicles.