Bring a large pan of water to the boil.
Add the noodles and cook for 2–3 minutes until just tender, then drain and set aside.
In a small bowl, whisk together the soy sauce, rice vinegar, sesame oil, chilli garlic sauce, sugar and water, then set aside.
Heat the vegetable oil in a large frying pan or wok over a medium heat until shimmering.
Add the garlic and cook for about 30 seconds, stirring constantly, until fragrant but not browned.
Add the drained noodles to the pan and pour over the sauce.
Toss with tongs for 1–2 minutes until the noodles are evenly coated and the sauce has thickened.
Divide between warm bowls and top with the spring onions.
Scatter over chilli flakes for extra heat, if you like.