The Yawning fits are related to carb loading, to borrow a runners term. If you don't spread out your carb intake, you will get too many carbs at one time and this can cause you to feel sleepy. Sometimes after dinner I fall asleep for a couple of hours, also due to carb loading.
"I get all flushed and feel like I'm lapsing into a sugar-induced coma"
If your numbers are still high you can still feel low. How can that be? The reason, blood glucose dropping rapidly can induce feelings of a low without you actually being low. So if you can't stand the feelings it causes then go ahead and treat it.
Eating a few crackers to eat will help the "low" feelings subside. In a few minutes you can return to normal activities. If blood glucose levels are not low, eating a carbohydrate snack is not urgent.
If in doubt, treat. If you think you may have low blood glucose but you can't do a blood test right away, get something sweet to eat. The treatment will not do any harm even if your glucose level is not low.
I hope this helps.