Remove the core and any wilted outer leaves from the cabbage, then cut it into very fine strips. Cut the onion and green bell pepper into thin strips as well. Use a large holed cheese grater to shred the carrots.
In a small bowl prepare the sauce by stirring together the soy sauce, brown sugar, sriracha, and corn starch.
Begin to cook the noodles according to the package directions (boil for 3 minutes, or until tender). Drain the cooked noodles in a colander.
Heat the vegetable oil over medium high heat in a large skillet until it is hot and shimmering. Add the vegetables and sauté for only a few minutes, or until the vegetables just begin to soften. Pour the prepared sauce into the skillet and continue to sauté for one to two minutes more, or until the sauce has thickened and coated all of the vegetables. Turn off the heat.
Add the cooked and drained noodles to the stir fried vegetables and toss to combine. Top with sliced green onions and a handful of fresh cilantro, if desired.