Heat the oven to 375°F. Lightly grease 8 cups of a standard muffin pan.
In a large mixing bowl, combine the ground beef, panko, egg, onion, chopped pineapple, pineapple juice, salt, pepper, and 2 tablespoons of the barbecue sauce. Mix gently until just combined.
Divide the mixture evenly among the 8 prepared muffin cups. Press it in lightly, leaving the tops slightly rounded.
Bake for 20 minutes. Carefully spoon off any excess liquid that has collected around the muffins.
Brush the tops with the remaining barbecue sauce. Bake for another 8 to 10 minutes, until cooked through.
Let the muffins rest in the pan for 5 minutes, then loosen the edges and lift them out to serve.