If that is a one time thing, ride it out (but drinking water will at least knock it down a bit)

If that is somewhat "common" then you need a new class of meds so see your doctor "soon" - sustained levels above 7.8 do all kinds of vascular damage that is cumulative so don't ignore it

Diet and exercise are very important.

For me, bicycling, walking, stair climbing, all bring down my numbers.

Drinking extra water can help a bit if you are dehydrated.

Insulin can help.