Preheat your oven to 500°F (260°C) and prepare a baking dish with cooking spray or parchment paper.

In a mixing bowl, combine ground chicken, panko breadcrumbs, crushed pineapple, milk, soy sauce, green onions, garlic, ginger, and black pepper. Mix thoroughly.

Form the mixture into golf ball-sized meatballs, yielding about 21 meatballs, and place them on the prepared baking dish.

Bake the meatballs for approximately 15 minutes, or until golden brown and reach an internal temperature of 165°F (74°C).

In a skillet, combine soy sauce, brown sugar, water, and reserved pineapple juice over medium heat. Stir in garlic and ginger until sugar dissolves.

Mix cornstarch with a bit of water to create a slurry, then stir into the skillet, simmering for about 5 minutes until thickened.

Remove meatballs from the oven and toss in the teriyaki sauce until well coated.

Serve immediately over rice or quinoa and garnish with additional green onions if desired.