The food was the only good thing about my last stay in hospital. Not that it was ideal for a diabetic, but it was hot and reasonably edible, and I could make my own sensible choices from the menu and decide for myself how much to eat.
After my last GTT I was given a completely inappropriate meal -- sweet coronation chicken on white bread, large banana, sweetened orange juice, biscuits, and jelly. And I was not allowed to leave until I'd eaten most of it. It got my sugar levels back up quickly... too quickly. They could have offered better given that most people having a GTT have some problem with glucose metabolism.
Having said that, I remember when my Dad was in hospital in the thirty years ago, sacharrine was the only artificial sweetener available. Hospital meals on the exchange diet were dire -- plain boiled potatoes, dry roasted meat, boiled unseasoned veg, a small salad without dressing, half a slice of bread, and orange sacharrine sweetened jelly with cabbage in it. Sugar, fat, and portions were limited but carbohydrates were not. Nasty. At least those days are gone.