Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a mixing bowl, combine the ground beef, breadcrumbs, milk, minced garlic, chopped green onions, beaten egg, salt, and black pepper. Mix until well combined.
Form the mixture into small meatballs, about 1 inch in diameter, and place them on the prepared baking sheet.
Bake the meatballs in the preheated oven for 15 minutes, or until they are browned and cooked through.
While the meatballs are baking, prepare the honey garlic sauce. In a medium saucepan over medium heat, combine the honey, soy sauce, rice vinegar, and crushed red pepper flakes (if using). Bring to a simmer and cook for 2-3 minutes, just until slightly thickened.
Once the meatballs are done, remove them from the oven and toss them in the honey garlic sauce until evenly coated.
Serve immediately, garnished with extra green onions if desired.