Heat the oil in a large skillet over medium-high heat.
Add the onion and garlic and cook until softened, about 3 minutes.
Stir in the ginger and red pepper flakes, if using.
Add the chicken and cook until heated through, about 5 minutes.
Add the noodles and toss to combine.
Stir in the soy sauce or tamari sauce, honey or brown sugar (if using), and sesame oil. Cook for another 2-3 minutes until everything is heated through.