Cook the udon noodles according to package instructions. Drain and set aside.
Heat the vegetable oil in a large skillet or wok over medium heat. Add the tofu cubes and cook until golden brown and crispy on all sides. Remove from the skillet and set aside.
In the same skillet, add the mixed vegetables and cook until they are tender but still crisp. Add the teriyaki sauce and stir to coat the vegetables.
Add the vegetable broth, soy sauce, rice vinegar, sesame oil, minced garlic, and minced ginger to the skillet. Stir to combine.
Bring the mixture to a simmer and cook for 5 minutes to allow the flavors to meld together.
Add the cooked udon noodles and crispy tofu cubes to the skillet. Toss gently to combine and heat through.
Serve the teriyaki tofu and vegetable udon hot, garnished with chopped green onions and sesame seeds.