Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large bowl, gently combine beef, breadcrumbs, eggs, onion, salt, and pepper. Form into 1-inch meatballs.
Arrange meatballs on the sheet and bake for 12–15 minutes until edges are just golden.
Meanwhile, whisk together pineapple juice, ketchup, rice vinegar, brown sugar, soy sauce, Worcestershire, and garlic in a saucepan over medium heat.
Once simmering, stir in the cornstarch slurry and cook 2–3 minutes until sauce thickens.
Add baked meatballs and pineapple chunks to the sauce. Gently toss to coat and warm through, about 5 minutes.
Transfer to a serving dish and garnish with thinly sliced green onions or toasted sesame seeds.