Bring a large pot of water to a boil over high heat. Add the noodles and cook until al dente according to the package instructions, about 3 minutes. Drain.
Meanwhile, in a small bowl, whisk together the soy sauce, oyster sauce, rice vinegar, brown sugar (if using), chili sauce, and water.
Heat the sesame oil in a large skillet over medium heat. Once the oil is glistening, add the garlic and ginger and cook, stirring often, until fragrant, about 1 minute.
Add the sauce to the pan and simmer for 3 to 4 minutes, or until slightly thickened. Stir in cooked ramen noodles until heated through and evenly coated in sauce, about 3 minutes.
Garnish with green onions and sesame seeds before serving.