Bring a pot of water to a rolling boil. Add soba noodles and cook according to package instructions (typically 4-5 minutes) until tender but firm. Drain and rinse under cold water.

In a small bowl, whisk together soy sauce, rice vinegar, and toasted sesame oil until well combined. Taste and adjust seasoning as needed.

Thinly slice the cucumber or spiralize it. Add to a bowl along with any additional vegetables like shredded carrots or bell peppers.

In a large mixing bowl, toss cooled soba noodles with cucumber and vegetables. Drizzle dressing over top and toss to coat evenly.

Serve immediately in chilled bowls. Optionally, chill in the refrigerator for up to a few hours before serving.