Cook the rice noodles according to package instructions. Drain and set aside.

In a large skillet or wok, heat the vegetable oil over medium-high heat. Add the sliced flank steak and cook until browned, about 3-4 minutes. Remove the beef from the skillet and set aside.

In the same skillet, add the minced garlic and ginger, cooking for about 30 seconds until fragrant. Add the red bell pepper and snap peas, stirring for 2-3 minutes until slightly tender.

In a small bowl, whisk together the soy sauce, hoisin sauce, brown sugar, rice vinegar, and sesame oil. Pour this sauce into the skillet with the vegetables and bring to a simmer.

Return the cooked beef to the skillet and add the drained rice noodles. Toss everything together until well coated in the sauce and heated through, about 2-3 minutes.

Serve immediately, garnished with sliced green onions and sesame seeds.