Why does my blood sugar spike after morning workouts?

Hormones: There are stress hormones and adrenalines that come out when you exercise. They counteract the effect of Insulin making it less effective, thus your blood sugar goes up. This is a natural response. Eventually, the blood sugar should come down as the Insulin become more sensitive again.

Sugar from the liver: When you exercise it frequently lowers glucose, but many are surprised to see the glucose rise. This especially happens if the glucose is somewhat high when you start to exercise. Also the great american breakfast is frequently carbohydrate rich and glucose rises are a problem anyway.

Reactive hyperglycem: Its actually common for diabetics (type i particularly) to have increased glucose reading during or right after physcial activity. This phenomon is commonly known as reactive hyperglycemia and is due to the counter regulatory hormone system (cortisol and growth hormone) that get activated during stress or physical activity. You should watch for low bs however during the few hours after cessation.

Hormones: During exercise, your body releases growth hormone, adrenaline, and cortisol. These hormones raise blood sugar. However, given the benefit of increasing muscle Insulin sensitivity, it's very common to see tighter control or low blood sugars for hours following exercise despite the transient high during or right after exercise.