In a small bowl, whisk together ¼ cup reserved pineapple juice, ketchup, brown sugar, and rice vinegar. Set aside.
¼ cup reserved pineapple juice, ¼ cup ketchup, ¼ cup packed light brown sugar, 1 tablespoon rice vinegar
Pat the chicken dry with paper towels. Toss with the cornstarch until coated. Dip into the beaten egg, then dredge in the flour. Shake off any excess.
1½ to 2 pounds boneless skinless chicken breast, 1 large egg, ⅓ cup cornstarch, ⅓ cup all-purpose flour
Heat ⅓ cup of oil in a large skillet over medium-high heat. Cook the chicken in batches, about 3 minutes per side, until golden and cooked through. The internal temperature should reach 165°F. Transfer to a paper-towel-lined plate.
⅓ cup oil
Discard the used oil. Add the remaining tablespoon of oil to the skillet. Add the onion and bell peppers and cook until slightly softened.
1 green bell pepper, 1 red bell pepper, 1 medium yellow onion
Stir in the garlic and ginger and cook for 1 minute. Add the pineapple chunks.
Pour in the sauce and cook over medium heat for 2 to 3 minutes until it thickens.
Return the chicken to the pan and toss to coat evenly in the sauce.
Garnish with sliced green onions and serve right away.
2 green onions
Notes
Store leftover sweet and sour chicken in an airtight container in the refrigerator for up to 4 days.
For longer storage, freeze the cooled chicken in a freezer-safe container for up to 2 months. Keep in mind that the coating will soften after freezing.
Thaw overnight in the refrigerator before reheating.
Reheat gently in a skillet over medium heat until warmed through. A splash of water helps loosen the sauce if it has thickened during storage. The microwave is convenient, though the chicken coating will be softer.
This recipe can be prepared ahead by chopping the vegetables, mixing the sauce, and cutting the chicken several hours before cooking. Store each component separately in the refrigerator until ready to cook.