Hot Dr. Pepper® The Dr. Pepper Museum is located in Waco, Texas. 12 ounces Dr. Pepper® 2 lemon slices Pour the Dr. Pepper® into a saucepan. Heat until it is hot and bubbly, at exactly 170 degrees F. Place a lemon slice in the bottom of each of two mugs. Pour the Dr. Pepper® into the mugs, then serve immediately.