Hi NELLBAT53
The short answer is yes. You will feel horrible after loads of sugar because massive amounts of insulin are dumped into the bloodstream to clear the excess of glucose as quickly as possible which means you end up being hypo (i.e. too far the other way).
I feel for you as I/my wife had an anniversary of the death of a family member a year ago too. If you are pre-diabetic, then I'm sure a day off won't hurt, but don't have too many lol.
For me, being pre-diabetic was a wake-up call. It made me do something about my diet. I have now lost a stone and a half in weight and going back to the doctor at the end of the month for a second fasting test.
This means you can do it too. Cut back on the carbs and sugar.