In a medium-sized bowl, combine flour, garlic powder, salt, and pepper. Add in your cubed chicken breasts and toss to coat the chicken pieces fully.
Place a frying pan on medium heat and drizzle in 2 tablespoon of oil. Add in your floured chicken pieces and fry, stirring occasionally, for 10 minutes until golden. Then remove and set aside.
In the same pan, add in your red and green bell peppers, and your onions. Fry for 3-5 minutes until slightly softened but still crunchy.
Add back in your chicken, give everything a toss, then turn off the heat.
Meanwhile, make your sauce. In a saucepan, combine ketchup, soy sauce, pineapple juice, rice wine vinegar, brown sugar, garlic, ginger, chicken stock and your cornstarch slurry. Place on medium heat and cook for 5-10 minutes until the sauce has thickened slightly to a saucy viscous consistency. Prepare your noodles according to packet instructions.
Once your sauce is ready, your chicken and veggies are cooked, and your noodles are ready, it's time to serve up. Divide your noodles between two bowls, then top with your fried chicken and veggie mixture. Top with as much sauce as you'd like. Sprinkle with sesame seeds and spring onions. Enjoy!