Trim off any visible fat and slice the beef into 1/4" thick strips against the grain. For easier slicing, freeze the beef for 30–60 minutes beforehand.

In a large bowl or zip-top bag, combine Dr Pepper, soy sauce, Worcestershire, brown sugar, black pepper, garlic powder, onion powder, smoked paprika, and red pepper flakes, if using. Stir well to dissolve the sugar.

Add the sliced beef to the marinade, making sure all pieces are coated. Seal and refrigerate for 12–24 hours. Flip or mix it once or twice during the marinade time for even coverage.

Remove the beef from the marinade and pat the strips dry with paper towels. This helps the jerky form a proper bark and reduces excess sugar from burning.

Preheat your smoker to 165–175°F. Use a mild wood like cherry, apple, or hickory. Lay the strips directly on the smoker grates or on jerky racks, making sure they don’t overlap. Smoke for 3–4 hours or until the jerky is firm, dark, and bends without breaking.