Step 1: Combine the Base Ingredients In a medium saucepan, combine ketchup, brown sugar, apple cider vinegar, Worcestershire sauce, and soy sauce. Whisk together until the mixture is smooth.Step 2: Add the Spices Add garlic powder, onion powder, paprika, black pepper, cayenne pepper, and mustard. Whisk well so the spices are evenly mixed into the sauce.Step 3: Add the Dr Pepper Slowly pour in 1 cup of Dr Pepper while stirring. Bring the mixture to a gentle simmer over medium heat.Step 4: Simmer and Reduce Reduce the heat and let the sauce simmer for about 20–25 minutes, stirring occasionally. The sauce will thicken as it cooks and the flavors will blend together.Step 5: Taste and Adjust Taste the sauce and adjust the flavor if needed. Add a little more brown sugar for sweetness, extra vinegar for tanginess, or more cayenne for heat.Step 6: Cool and Store Remove from heat and allow the sauce to cool to room temperature. Transfer it to an airtight jar and store it in the refrigerator for up to 2 weeks.