In a mixing bowl, combine the ground turkey, panko breadcrumbs, egg, minced garlic, and ¼ cup of the teriyaki sauce. Mix until the ingredients are evenly distributed.
Shape the mixture into 16 to 20 meatballs of similar size and place them in the slow cooker.
Add the drained pineapple chunks and the remaining ½ cup of teriyaki sauce to the slow cooker. Gently stir to coat the meatballs.
Cover and cook on low until the meatballs are cooked through.
Stir in the snow peas during the final portion of cooking so they soften slightly but retain their texture.
Serve the meatballs, pineapple, and snow peas over cooked rice and top with the sliced green onions.