Stress and poor sleep can also cause high blood sugars. So can intense work outs. Basically anything that triggers cortisol that then triggers creation of glucose.
Couple of strategies I employ, other than managing stress and getting 7-8 hours sleep every day: get as low as you can on carbs, even go carnivore for awhile , and move to intermittent fasting. Once a week, do a 36 hour fast minimum, and work to improve that to 72 hours.