Heat a smoker to 250°F using the manufacturer-recommended amount of oak or hickory smoking wood. Lightly oil an oven-safe perforated grill tray.
Soak saltine crumbs in milk for 5 minutes. Stir in eggs, onion, Worcestershire, salt, pepper and garlic powder, then fold in beef.
Shape a 9-by-5-inch loaf about 2 1/2 inches high on the grill tray. Place in the smoker over indirect heat.
Smoke for 120 minutes, maintaining 250°F. Stir tomato sauce, molasses, vinegar and mustard together.
Brush the sauce over the loaf and smoke for 30 to 60 minutes more until the center reaches 160°F; use temperature rather than color to judge doneness.
Rest for 15 minutes before cutting into 8 slices.