Frequently Asked Questions about Diet Coke and Caffeine Does Diet Coke have caffeine? Yes, Diet Coke does contain caffeine. However, the amount of caffeine in Diet Coke is significantly less compared to regular Coke. A 12-fluid ounce can of Diet Coke contains around 46mg of caffeine. Click here to learn more about the caffeine content in Diet Coke. How much caffeine does Diet Coke have? A 12-fluid ounce can of Diet Coke contains approximately 46 milligrams of caffeine. It is considerably lower than the caffeine content found in regular Coke or other caffeinated beverages. Visit this page for more information…