[t2dthrowaway]

As someone who has come quite close to reversing their T2D, I will say that as I've lowered my a1c (the main measure of diabetes) and dropped from 3 drugs to 1, I've noticed two things from blood sugar monitoring: not only have overall sugars gone down drastically, but the time to recover from "cheating" has greatly decreased as well. When I was at my worst, I couldn't even eat a piece of fruit without a huge sugar spike. After 3 years on a lower carb, calorie constrained diet (~130g carb/day and ~1900 calories), combined with some exercise, I can now eat an occasional small piece of cake or the like without a huge concern. My sugar will spike for an hour or two, but then normalize. Before i might be high for almost a day before I'd drop back to my baseline.

So it does improve, but it's unlikely to completely go away. In my case it's likely from improved insulin resistance.

To answer your question, I wouldn't say it "crashes" back. It's still a concern, but if it's controlled, you can eat some cake and cookies and you'll stabilize in a few days. It's when it's a long term habit, that it's uncontrollable (at least on my case study of one).