I do wonder what his appeals process is for this. AFAIK, the prison has its own internal prisoner review process, which stops at the Chief Admin/Warden. "I want two fruit cups, due to nutritional needs, they only gave me one." Is a few missing fruit cups or lack of extra bread roll enough to make management talk to the prisoners who are in charge of putting stuff on plates? If there are still "mistakes" then what's his appeal process?
How would he even manage to file a lawsuit against the prison/its admins? I mean, sometimes you see the defense attorney from the criminal trial attempt to redress truly egregious prison conditions, but that's actually rare. In this case, he had a public defender, and I really don't think they're going to go against their own public system to get him his fruit cup.
But let's say that a hungry civil attorney, wanting notoriety, decides to file a lawsuit against the prison and names the State of Idaho as a defendant. To get said civil attorney, BK needs permission from...the Chief/Warden (who approves all visitors and phone call participants who are not immediate family). Let's say the Warden says "Nope," you lost your right to make outside business arrangements when you became a convicted felon.
I can't even imagine a system in which prisoners were all allowed to have civil attorneys stop by and then file suits on their behalf. I have no clue if this happens at all, but I know it's not common.
Warden will likely tell kitchen admin (who doesn't themselves perform the tray filling) to give BK his extra (vegan) fruit cup, as he is entitled to stay on his vegan food plan.
(I imagine he's getting things like a can of drained black beans dumped on top of the standard prison "salad"...plus a fruit cup).
He's entitled to a certain number of calories spread across the traditional categories (protein, carbs, fats). I doubt his micronutrient balance and vitamins are going to be studied by some in-prison health crew. If he wanted freedom to eat as he wishes, he ought not to have done something to land in prison?
IMO.