how much caffeine is in a diet dr. pepper can
Best Answer: Regular Dr Pepper = 28 mg of caffeine per 8 fluid ounces. Diet Dr Pepper = 28 mg of caffeine per 8 fluid ounces. Diet Cherry Vanilla = 26 mg of caffeine per 8 fluid ounces. Regular Cherry Vanilla = 26 mg of caffeine per 8 fluid ounces.