Preheat the oven to 375 degrees F. Grease a 9x13-inch baking dish with nonstick spray.
Pour chicken nuggets into the prepared pan and spread out evenly in one single layer.
Whisk the sugar, ketchup, vinegar, soy sauce, and garlic salt together in a medium bowl until combined. Pour sauce evenly over the frozen chicken nuggets in the dish.
Bake uncovered for 25 to 28 minutes or until hot and bubbly (stirring the chicken once halfway through the bake time.) Serve warm and enjoy!