Slice all the vegetables into thin matchsticks. I like them all nice and thin. Gather everything in a large bowl.
Prepare the vegetables up to 1 day in advance.
Bring a large pot of water to a boil. Add noodles & cook for 5-6 mins. Immediately drain & rinse under cold water to prevent overcooking.
While noodles are cooking, in a small bowl, whisk together soy sauce, rice vinegar, honey & sriracha, if using.
In a bowl, toss all the vegetables until well combined. Then toss it with buckwheat noodles and the dressing. Serve right away, or refrigerate.