I agree with Teena's comments about the coffee itself. I can drink diet coke or put sweetener on something and my blood sugars are not impacted. But a lot of black coffee in the morning and my blood sugars go up.
As evidence, I'll check my blood sugars first thing in the morning and be, say, at 5.9. If I bring a travel mug full of coffee on my 1/2 hour drive to work, when I check my sugars again (with no food yet in my stomach at this point), I'll often be up around 8 or 9. The only thing I can blame is the coffee.