In a large measuring cup, add soy sauce, rice vinegar, ketchup, brown sugar, sweet chili sauce, sriracha sauce, and red pepper flakes. Stir until well combined.
Dredge coated chicken pieces in corn starch. Repeat with all chicken.
Heat oil in a large skillet or frying pan over medium high heat.
Place chicken pieces in hot oil and fry for 2 minutes on each side. (Fry in batches to avoid overcrowding).
Remove chicken and place on paper towels to absorb excess oil. Repeat with remaining chicken.
Remove oil from the pan and add sauce. Simmer on low until the sauce thickens.
Add peppers, onions, and chicken. Toss to evenly coat and summer for 3 to 4 minutes.
Serve over ramen noodles or cooked rice.