Start by cutting the chicken breasts into bite-sized pieces. Coat the chicken evenly with cornstarch. This will give it that signature crispy texture once fried. Set the coated chicken aside.

In a large pan or skillet, heat the vegetable oil over medium-high heat. Once hot, add the coated chicken pieces to the pan. Fry them in batches if needed to avoid overcrowding. Cook for about 4-5 minutes per side until golden brown and crispy. Once done, remove the chicken from the pan and set it aside on a plate lined with paper towels to drain excess oil.

In the same pan, add a little more oil if needed. Toss in the bell peppers and onions and stir-fry them for about 3-4 minutes until they’re tender but still crisp. Add the pineapple chunks and cook for another 2 minutes to warm through.

In a small bowl, whisk together the soy sauce, rice vinegar, ketchup, sugar, garlic, and ginger. Pour this sauce into the pan with the veggies. Let it simmer for about 2-3 minutes until the sauce thickens slightly.

Return the crispy chicken to the pan with the sauce and vegetables. Toss everything together to coat the chicken in the sweet and sour sauce. Stir for another 2-3 minutes until everything is well combined and heated through.

Once your sweet and sour chicken is ready, serve it immediately over steamed rice or alongside your favorite stir-fried vegetables. Enjoy the perfect balance of crispy, tangy, and sweet!