In a bowl, add the water, then add the noodles, soak for 15 minutes or until soft. Use the kitchen sears, cut the noodles into shorter strands. Set it aside.
Make the sauce. In a bowl or measuring cup, add soy sauce, oyster sauce, rice vinegar, and brown sugar. Use a whisk, mix until the sugar is dissolved.
Heat a wok or wide pan with oil, over medium heat. Add the onion, cook for a minute or until tender. Add the garlic, saute for a minute or until fragrant.
Add all the veggies, except green onions. Saute until tender.
Add the chicken, continue stirring until well heated. Add the shrimps, cook until they turned pink.
Add the noodles and the sauce. Keep stirring until well combined, and the noodles had soaked up the sauce. Drizzle sesame oil and garnish with green onions. Serve warm.