Marinate the Chicken:
Toss chicken with soy sauce, cornstarch, salt, and pepper. Let sit for 10 minutes while prepping other ingredients.
Make the Sauce:
In a bowl, whisk together pineapple juice, soy sauce, ketchup, vinegar, brown sugar, and cornstarch slurry. Set aside.
Cook the Chicken:
Heat oil in a large skillet or wok over medium-high heat. Add chicken and stir-fry for 5–6 minutes until golden and cooked through. Remove and set aside.
Stir-Fry Vegetables and Pineapple:
In the same pan, add bell peppers, garlic, and ginger. Cook for 2–3 minutes until slightly tender. Add pineapple chunks and sauté for 1 more minute.
Combine and Add Sauce:
Return chicken to the pan. Pour in the sauce and toss everything to coat. Cook for 2–3 more minutes until the sauce thickens and glazes the chicken.
Serve:
Serve hot over steamed rice or noodles. Garnish with green onions and sesame seeds if desired.