what do doctors call the bland diet to eat something for every letter all I can remember is not to eat toast?

The only thing that comes to mind is the BRAT diet, although it doesn't match your description 100%. Google it to see if that's what you're thinking of.

I had a roommate who was (still is) a dietitian in a big NYC hospital. She'd refer to a "bland diet" for some patients which consisted of jello, broth, some other stuff that didn't tax the digestive system too much (and had very little seasoning to it).

I've never heard of a bland diet for diabetics since hot sauce, herbs, spices are generally encouraged since they don't tend to raise blood glucose, they make food very flavorful. They do advise diabetics, and all people in general, not to eat "white" foods--since most white foods have been highly processed taking away a lot of the fibrous material that actually helps us. Thing like white bread and white potatoes and white pasta and white cake flour, etc.