Yes, Diabetes can be reversed, albeit briefly through some specific interventions.
Diabetes can be broadly classified into Type 1 Diabetes (T1DM) and Type 2 Diabetes (T2DM), although different other types like MODY (maturity onset diabetes in young) and LADA (latent autoimmune diabetes in adults) have been identified lately. I would limit my discussion to the former types.
Type 2 Diabetes can achieve remission in the early stages by incorporating medical nutrition therapy and exercise in our daily routine. Consumption of Mediterranean diet/Dietary approaches to stop hypertension (DASH) diet along with 150 min per week of moderate intensity structured physical activity can lead to partial reversal of Type 2 Diabetes.
Bariatric surgery (done for morbid obesity) can revert back Type 2 Diabetes in 23-60% of cases depending on the baseline duration and severity of diabetes. However, it might not be effective in advanced stages of Type 2 Diabetes and chance of recurrence is substantial in the long-term who initially respond.
On the other hand, Type 1 Diabetes can only be reversed by successful SPK (simultaneous pancreas and kidney transplantation -done in handful of centres in India) or Islet transplantation (even rarely performed).
Drug or stress induced hyperglycemia wanes off in most cases if inciting entity vanishes.