Combine the rice vinegar, 2 tablespoons of the soy sauce, sesame oil, and sriracha in a bowl. Taste, and add more sriracha if you'd like. Add the chopped water chestnuts, cabbage, and carrots to marinate slightly.
Meanwhile, heat a pan with a drizzle of oil or cooking spray to medium heat. Cut the tofu into small cubes, and toast lightly in the pan for 10 minutes or so, shaking every once in awhile. When the tofu is browned on all sides (give or take, don't obsess too much), drip in the remaining teaspoon of soy sauce. Toss to combine.
To the veggie/dressing mixture, add the cooked quinoa, tofu, scallions, and sesame seeds. Stir together, and taste: add more soy sauce if you'd like.
Serve as a complete meal or with your favorite Asian veggie side dishes. Enjoy!