Preheat your oven to 325°F (165°C) and line a 13×9-inch baking pan with parchment paper. Set aside.
Season the chicken pieces with salt and pepper. Place the cornstarch in a large resealable plastic bag, add the chicken, and shake to coat evenly.
In a shallow bowl, beat the eggs. Heat the vegetable oil in a skillet over medium-high heat until shimmering.
Dip each chicken piece into the beaten eggs, then sear in the hot skillet until golden brown on all sides. Transfer the seared chicken to the prepared baking pan.
In a medium bowl, whisk together the sugar, ketchup, apple cider vinegar, soy sauce, garlic powder, and sea salt until smooth.
Pour the sweet and sour sauce evenly over the chicken in the pan.
Bake in the preheated oven for 1 hour, tossing the chicken halfway through baking to ensure even coating and caramelization.
Remove from the oven and serve hot, optionally garnished with chopped green onions or sesame seeds.
Enjoy!