 Which one of these coffees gives you the biggest caffeine buzz? Well, it's not this one. As the cheapest on the list, you might get what you pay for at only about 9 mg of caffeine per ounce. America might run on it, but at only 15 mg of caffeine, we could run a little faster. This is the best bang for your buck at 17.5 mg, meaning you could get a 280 mg caffeine boost in their regular cup for less than $2. Starbucks will have to settle for number two, at least caffeine-wise, at about 19 mg per ounce. And the number one most caffeinated coffee on our list is? It has almost 21 mg of caffeine per ounce, or 416 in their largest cup.