Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper or a silicone mat.
In a large mixing bowl, combine ground meat, breadcrumbs, egg, minced garlic, salt, and black pepper. Mix everything together with clean hands or a spoon until well integrated.
Form the mixture into evenly sized meatballs, about 1 to 1.5 inches in diameter, and place them on the prepared baking sheet.
Bake the meatballs in the preheated oven for about 15-20 minutes, or until they are browned and cooked through, with juices running clear when pierced.
While the meatballs bake, combine soy sauce, brown sugar, apple cider vinegar, and ketchup in a small saucepan. Whisk over medium heat until the sugar dissolves and the sauce begins to simmer with a slight bubbling around the edges.
Allow the sauce to simmer gently for 5-7 minutes, stirring occasionally, until it thickens into a glossy, sticky glaze with a vibrant tangy-sweet flavor.
Transfer the baked meatballs into the skillet with the glaze, and gently toss to coat each meatball evenly with the sauce.
Cook the coated meatballs in the sauce over low heat for an additional 5 minutes, allowing the glaze to set and cling to the meatballs with a shiny finish.
Serve the vibrant, glossy meatballs hot, with some extra sauce drizzled on top if desired, alongside rice or steamed vegetables for a complete meal.