Preheat oven or outdoor grill to 350 degrees F.

In a 12-inch cast iron skillet, cook the bacon over medium heat. Once about half cooked, about 3 minutes, add the onions and cook on medium low heat for 8 minutes. Add the garlic and saute for 30 seconds.

Add the tomato sauce, Dr. Pepper, barbeque sauce, molasses, Worcestershire sauce, vinegar, and mustard powder. Stir to combine and bring to a simmer. Add the beans and bring to a simmer. Cook in the oven or on the grill, stirring occasionally, until the flavors meld and the sauce thickens, about 20 minutes. Taste and season with salt and pepper, as needed.