aw, poor little guy. Kitties are literally starving when their blood sugar is high. The glucose that should be nourishing every cell in their body is floating about in the blood stream instead of getting into the cells.
After punkin vomited, for any reason, I would give him about a teaspoonful of food (with some water) every 20 minutes or so. He hated waiting for it, but it's better than having them barf again.
Do try to get a ketone test when you can - ketones can appear at any blood sugar, but anytime kitties are high, we start worrying about it.