Diet.
I agree with diet. Works like a charm, and costs nothing. Keep total carbs below 20 to 100 grams, max. a day, and no worries with type 2, and much better for type 1.
Something that bothers me is the focus on glucose - and neglecting the more important role played by insulin and insulin resistance. Dr. Jason Fung is a good doc to research... https://www.doctorjasonfung.com/the-diabetes-code for those who might be interested.
I wonder if it is because glucose is quicker and easier to test than the long time (2 to 3 hours) to evaluate how insulin behaves after eating.
I suspect it is cost and time, rather than treating the underlying disease process, focusing instead on the symptoms. But, I could be wrong, of course.