I only looked for studies on the effect of exercise, there may be more in regards to dietary changes.
The impact of brief high-intensity exercise on blood glucose levels is a review article analysing several articles on this subject, with studies in both patients with and without diabetes.
One looked at two weeks of exercise:
Two weeks of sprint interval training increased insulin sensitivity up to 3 days postintervention
Original study: Short-term sprint interval training increases insulin sensitivity in healthy adults but does not affect the thermogenic response to beta-adrenergic stimulation
Others looked at single training sessions of high intensity interval training (HIIT):
low volume SIT with as little as 7.5 minutes of high-intensity exercise per week may be a time-efficient exercise strategy to help control blood glucose in diabetic patients and improve insulin sensitivity in nondiabetic adults.
However, this is a brief effect:
it is [...] uncertain if any improvements in blood glucose achieved by a brief intervention would be sustained over a longer period
But there does seem to be a short-term effect for training at high intensities that does not need to be sustained for long - typical exercise duration in these studies was a couple of sprints at a few minutes of high intensity training per session plus warm up.