I do have some orange juice most mornings, but then I drink water or coffee the rest of the time. I think that any diet that is just one thing is likely to be bad. I go for a mix and that will include some sweet treats. I assume my exercising will burn off some of that.
I hope your friend can get on a better path. It seems diabetes is really common now in the richer countries as bad foods are so cheap and available.
He is doing great so far but based on how his life has always been I would imagine as soon as he gets the green light from his doctor saying that the situation has improved that he will immediately return to his old habits that got him to this position in the first place. I'm going to try to encourage him not to do that and will ask my other fitnessy friends to do the same.