So why are so many people addicted to Starbucks? There is nothing extraordinary in their coffee beans, and no special coffee or extra ingredients that that produce addition aside from caffeine.
On average, an espresso contains around 63 milligrams of caffeine per ounce. Starbucks serves 75 milligrams of caffeine in each of its .75-ounce espresso shots. Dunkin Donuts claims a hefty 118 ...