Heat vegetable oil in a large skillet or wok over medium-high heat.
Add minced garlic and stir-fry for about 30 seconds until fragrant.
Add chicken strips and cook until browned and cooked through, about 5-7 minutes.
Push chicken to one side of the skillet. Add mixed vegetables to the other side and stir-fry until crisp-tender, about 3-4 minutes.
Combine chicken and vegetables in the skillet. Pour in teriyaki sauce and soy sauce.
Stir everything together and simmer for another 1-2 minutes until heated through and sauce thickens slightly.
Serve hot over cooked rice. Garnish with sesame seeds and sliced green onions.