Cut the chicken into bite-sized pieces and coat with cornstarch.
Deep-fry the chicken until golden brown and crispy.
Heat a pan with a little oil and sauté garlic until fragrant.
Add pineapple juice, ketchup, rice vinegar, soy sauce, and sugar to make the sweet and sour sauce.
Simmer the sauce until slightly thickened.
Add the fried chicken and toss until evenly coated in the sauce.
Serve hot with steamed rice, garnished with sesame seeds or green onions if desired.