Toss diced chicken with teriyaki sauce and set aside to marinate.
Heat 1 tablespoon oil in a wok over medium-high heat.
Add chicken and cook until fully cooked and lightly caramelized.
Remove chicken from pan and set aside.
Add remaining oil and sauté garlic until fragrant.
Add mixed vegetables and stir-fry for 2–3 minutes.
Push vegetables to one side and scramble eggs in the pan.
Add cooked rice and stir to combine with vegetables and eggs.
Return chicken to the pan and mix well.
Add soy sauce, black pepper, and sesame oil.
Stir-fry for 2–3 minutes until heated through.
Garnish with green onions and serve hot.