Preheat oven to 325 degrees F (165 degrees C). Wrap tortillas in foil.
Heat a large skillet over high heat until very hot. Add pork, onion, ginger, and garlic; cook and stir until pork is brown and onion is tender, about 5 minutes. Mix in bok choy, red bell pepper, and mushrooms; cook and stir until bell pepper is tender-crisp, about 5 minutes. Remove pan from heat.
Place tortillas in oven for 8 minutes, or until warm.
Meanwhile, return pan to high heat source, and mix in bean sprouts, sake, and hoisin and soy sauces; cook and stir until bean sprouts are tender-crisp, about 5 minutes.
Remove tortillas from oven. Divide pork mixture among tortillas, and roll up. Serve immediately.
