Coat chicken breasts with baking soda and let sit for 15-20 minutes. Rinse with cold water and pat dry.
Heat avocado oil in a pan over medium heat. Add the chicken and sauté until browned and cooked through. Remove from the pan and set aside.
In the same pan, add more oil if needed and stir fry the sliced green and red bell peppers, broccoli, and white onion until tender.
In a small bowl, whisk together the teriyaki sauce ingredients: soy sauce, chicken broth, white sugar, rice vinegar, grated garlic, onion powder, sesame oil, Sriracha, white pepper, and oyster sauce.
Return the chicken to the pan and pour the teriyaki sauce over the chicken and vegetables. Cook until the sauce thickens and coats the chicken and vegetables.
Serve the teriyaki chicken over cooked udon noodles. Garnish with sesame seeds and enjoy!