Heat vegetable oil in a large pot to 350°F for deep frying.
In a bowl, whisk together eggs, cornstarch, and flour to create a smooth batter.
Coat chicken chunks in the batter, ensuring each piece is well covered.
Carefully fry chicken pieces in hot oil until golden brown and crispy, about 4-5 minutes. Remove and drain on paper towels.
In a large pan, sauté bell peppers, onion, and pineapple over medium-high heat for 3-4 minutes until slightly softened.
In a small saucepan, combine sugar, brown sugar, apple cider vinegar, ketchup, soy sauce, and minced garlic.
Bring sauce mixture to a simmer and cook for 5-7 minutes until thickened.
Add the crispy fried chicken to the pan with vegetables.
Pour the thickened sauce over chicken and vegetables, tossing to coat evenly.
Serve immediately while hot and crispy.