The highest post-meal reading (2hrs) I've had is 178. I was really stressed out that day and didn't have a good nights sleep. I had 2 cans of soda which were loaded with Sugar and caffeine.
It's definitely high cortisol that causes high blood Sugar in my case. Laredo is right. It's nothing to worry too much about as it's a side effect due to high cortisol which is causing the insulin resistance or a congested liver causing blood Sugar instability but you do need to cut down on sugars and starches until you can normalise your cortisol levels and continue to monitor your blood sugar just in case.
My fasting blood sugar is fine at an average of 80 but can be unstable throughout the day, especially if I eat sugary/starchy foods and haven't had enough sleep.
When I am well rested, I can eat sugary stuff and drink sodas and my blood sugar readings are fine.