Prepare the chicken: Cut 1 lb of boneless chicken breasts into 1-inch pieces. Preheat your oven to 325°F (163°C).
Prepare the baking dish: Coat a baking dish (9x13 inch) with nonstick spray to prevent sticking.
Make the sauce: In a bowl, mix together ¼ cup ketchup, ½ tsp garlic powder, ¾ cup sugar, ½ cup apple cider vinegar, and 1 tbsp soy sauce. Set this sauce mixture aside for later use.
Season the chicken: In a mixing bowl, season the chicken pieces with salt and pepper to taste. Then, toss them in ½ cup of cornstarch until evenly coated. This will help achieve a desirable crunch.
Dip in eggs: Next, dip the cornstarch-coated chicken pieces into 2 beaten eggs, ensuring that each piece is thoroughly coated.
Fry the chicken: Heat ¼ cup of oil in a pan over medium heat. Once hot, add the chicken pieces. Cook them for 1-2 minutes on each side until they are golden brown. Afterward, drain them on paper towels to remove excess oil.
Bake: Place the fried chicken pieces in the prepared baking dish. Pour the sweet and sour sauce over the chicken, tossing to coat the pieces evenly. Bake in the preheated oven for about 50 minutes, flipping the chicken after the first 15 minutes to promote even cooking.
Garnish and serve: Once baked, garnish the dish with sliced green onions for added color and flavor. Your Baked Sweet and Sour Chicken is now ready to serve!