Use the Dr Pepper to deglaze the pan. Scrape all of those wonderful brown bits off the bottom of the pan with a wooden spoon. Drain and rinse the beans and then add them to the onions. Throw in everything else – molasses, brown sugar, ketchup, Worcestershire, dry mustard, garlic, salt and pepper.
Bring to a boil on the stove then cover and cook in a 350° oven for 20 to 30 minutes, depending on how thick you like it. If you prefer soupier beans, take them out after 20 minutes.