Step 1: Coating the Chicken: Place the cornstarch in a shallow bowl and the beaten eggs in another. Dip each chicken cube into the cornstarch until fully coated, then dip it into the egg wash. This double coating ensures the chicken stays juicy inside while getting crispy outside.
Step 2: Frying the Chicken: Heat the vegetable oil in a large skillet over medium-high heat. Add the chicken in batches, making sure not to crowd the pan. Fry until the chicken is golden brown and cooked through, about 3-4 minutes per side. Remove the chicken and set it aside on a paper towel-lined plate.
Step 3: Preparing the Sauce: In a medium mixing bowl, whisk together the sugar, ketchup, apple cider vinegar, soy sauce, and garlic powder. Stir until the sugar is mostly dissolved and the mixture is smooth and vibrant red.
Step 4: Sautéing the Vegetables: Wipe out most of the oil from the skillet, leaving about a tablespoon. Add the bell peppers and onions. Sauté for about 3-5 minutes until they are slightly softened but still have a bit of a crunch.
Step 5: Combining and Thickening: Add the fried chicken and pineapple chunks back into the skillet with the vegetables. Pour the sauce over everything. Stir constantly over medium heat for 2-3 minutes until the sauce thickens and coats every piece of chicken and vegetable evenly.