Boil noodles for 1 minute less than package's instructions, about 3 minutes. Immediately drain and toss in a little oil to keep them from sticking together.
In a small bowl, dissolve the sugar and salt in the hot water. Then add the soy sauces, oyster sauce, sesame oil, vinegar, and white pepper. Stir to combine.
Heat wok the wok until just smoking. Pour in 1/2 of the oil around the sides. Stir fry the onions, light green part of chives (or white part of scallions) and mushrooms until soft, about 5 minutes. Add cabbage and red bell pepper. Stir fry until soft, about 3-5 minutes.
Add 1 tbsp oil and noodles. Stir fry everything until noodles get warm, 30 seconds. Spread sauce mixture over everything and gently stir-fry for 1 minute to distribute evenly. Add another tablespoon or two of oil if noodles are sticking together.
Add remaining chives and mix until the are bright green and noodles are heated through, about 1 to 3 minutes.