Bring a large pot of lightly salted water to a boil; add bean sprouts and cook, uncovered, until tender yet still crisp, about 15 seconds. Drain in a colander, then immediately immerse in ice water for several minutes to stop the cooking process. Drain well and set aside.
Whisk sesame oil, soy sauce, Korean chile powder, sesame seeds, and garlic together in a large bowl. Stir in bean sprouts and toss to coat; sprinkle with green onions and season with rice wine vinegar. Refrigerate before serving.