Port City Java is a great place for a quick (but sometimes not so quick, depending on the length of the line and how many feel like fumbling with cash early in the morning).... coffee. It's located in front of Hearst Tower on N. Tryon and also has a mobile cart in the inside of Hearst Tower.
It's definitely your no-frills coffee place where you'll maybe get a smile from the barista, but the coffee here is reasonably priced, freshly brewed, and tastes great. I've gotten both brewed coffee and espresso here and have not been disappointed.
Note that Port City Java doesn't really have any "healthy" breakfast options - they have a decent selection of pastries and baked goods and the only oatmeal they have is essentially instant oatmeal in a cup, which they add water to. It's over $3 if I recall, for some instant, albeit tasty, oatmeal.
Port City is great for anyone working in or near the Hearst Tower and the Fifth-Third building