Preheat the oven to 350°F.
In a large bowl, combine ground beef, breadcrumbs, onion, garlic, Worcestershire sauce, soy sauce, ginger, eggs, milk, and pepper. Mix until just combined.
Shape the mixture into 1-inch balls and place on a parchment-lined baking sheet. Bake for 20-25 minutes or until cooked through.
In a saucepan, combine pineapple juice (drained from the chunks), brown sugar, honey, red pepper flakes, rice vinegar, and soy sauce. Heat over medium until boiling.
Mix cornstarch and water in a small bowl. Gradually whisk the slurry into the boiling sauce. Add peppers and allow the sauce to thicken.
Add pineapple chunks to the sauce. Return to a boil, then reduce heat and simmer for 1 minute. Add baked meatballs to the sauce, stirring to coat.
Serve hot with sesame seeds sprinkled on top.