In a bowl, add the noodles and 2 cups of water or until the noodles are all covered. Soak for 15 minutes. When the noodles softened, use the kitchen sears and cut the noodles into shorter strands.
Meantime, in a bowl, add the beef slices and all the marinade ingredients. Toss to coat well, and marinate for 5-10 minutes.
Heat a wok or wide pan with oil. I use a wooden spoon to test my oil if it's hot enough. Dip the spoon into the oil, if you see bubbles forming at the tip of a spoon, it means the oil is ready.
Add the marinated beef into the pan, and cook for 2 minutes on each side or until browned and well seared. Remove from the pan and set them aside.
Use the same pan, add more oil if the pan is drying. Add the onion, and saute until tender. Add the garlic and ginger, and continue sauteing until fragrant.
Add the bell pepper, and cook until tender. Add the cooked beef and the teriyaki sauce into the pan, and stir to combine. Add the softened noodles, and continue stirring until coated with the sauce.
To finish, sprinkle green onions and sesame seeds on top. Serve immediately.