Begin by cooking the rice noodles according to package instructions. Drain and set aside.
In a bowl, combine the soy sauce, oyster sauce, brown sugar, sesame oil, and chili flakes if using. Mix well and set aside.
Heat the vegetable oil in a frying pan or wok over medium-high heat.
Add the sliced beef and stir-fry for about 3-4 minutes or until the beef is browned and cooked through. Remove the beef from the pan and set aside.
In the same pan, add the minced garlic, grated ginger, bell pepper, and half of the green onions. Stir-fry for about 2-3 minutes until the vegetables are tender.
Return the cooked beef to the pan and pour the sauce mixture over the beef and vegetables. Stir well to combine.
Add the cooked rice noodles to the pan, tossing everything together to mix well and heat through for an additional 2-3 minutes.
Serve the Sticky Beef Noodles in bowls, garnished with the remaining green onions and fresh cilantro.