Preheat the oven to 400°F (200°C). Line a baking tray with parchment paper.
In a large mixing bowl, combine ground chicken, breadcrumbs, green onions, crushed pineapple, egg, soy sauce, sesame oil, garlic powder, ginger powder, salt, and pepper. Mix until well combined.
Form the mixture into 1-inch meatballs and place them on the prepared baking tray.
Bake the meatballs in the preheated oven for 20 minutes or until cooked through and golden brown. You can check the internal temperature for doneness; it should reach 165°F (74°C).
While the meatballs are baking, prepare the teriyaki sauce. In a small saucepan, combine soy sauce, brown sugar, rice vinegar, cornstarch, and water. Whisk together over medium heat until the sauce thickens, about 5 minutes.
Once the meatballs are done, remove them from the oven and place them in the frying pan or skillet. Add the teriyaki sauce and pineapple chunks, gently tossing to combine.
Cook on medium heat for an additional 5 minutes, allowing the meatballs to absorb the sauce.
Serve hot, garnished with additional green onions or sesame seeds if desired.