1-Prepare all ingredients: Prepare all ingredients by cutting the chicken into bite-sized pieces, as specified with 1¼ pounds boneless skinless chicken breasts or thighs, slicing bell peppers, and preparing pineapple chunks to keep everything organized.

2-Mix the sweet and sour sauce: Mix the sweet and sour sauce by combining 1/4 cup fresh pineapple juice, 2 cloves minced garlic, 2 tablespoons water, 2 tablespoons apple cider vinegar (rice vinegar can substitute), 1 tablespoon low sodium soy sauce, 2 tablespoons brown sugar, 2 tablespoons ketchup, and 1 tablespoon cornstarch in a small saucepan. Simmer on low heat until slightly thickened, whisking frequently, then cover and remove from heat.

3-Coat and cook the chicken: Place the 1¼ pounds of chicken pieces in a large bag with 1/3 cup cornstarch and shake to coat. Heat 2-3 tablespoons vegetable or canola oil in a large skillet over medium-high heat, add the coated chicken, and cook until browned and cooked through, about 4-5 minutes. Remove the chicken from the skillet.

4-Cook the vegetables: Add additional oil if needed, then cook 1 medium onion cut into large dice for 1-2 minutes. Add 1 green bell pepper seeded and cut into large dice and 1 red bell pepper seeded and cut into large dice, and cook for 2-3 minutes until slightly tender.

5-Combine chicken and vegetables: Reduce the heat to low, return the cooked chicken to the skillet, and cook for 1 minute to combine.

6-Finish with sauce and pineapple: Pour the prepared sauce over the chicken and vegetables, then add 1½ cups fresh pineapple chunks, 2 pinches red pepper flakes, and salt and pepper to taste. Stir gently and warm through before serving immediately over cooked rice or Chinese noodles.