Heat the oven to 400°F. Lightly grease 8 cups of a standard muffin tin.
In a large bowl, combine the ground beef, panko, egg, onion, pineapple, ginger, garlic, and 2 tablespoons of the teriyaki sauce. Mix gently until just combined, taking care not to compact the meat.
Line each prepared muffin cup with one slice of bacon, pressing it around the inside edge. Divide the meat mixture among the cups and press it in gently. Fold any excess bacon over the tops.
Bake for 20 minutes, until the meatloaf muffins are mostly cooked through. Carefully spoon off any excess fat from the cups.
Brush the tops with the remaining 2 tablespoons of teriyaki sauce. Bake for another 5 to 8 minutes, until the bacon is browned and the centers reach 160°F.
Let the muffins rest in the tin for 5 minutes, then lift them out carefully. Sprinkle with sliced green onions before serving.