Stir together vinegar and sugar in a medium bowl. Add grapes, cucumber, carrots, radish, and jalapeno; cover and refrigerate for at least 1 hour, stirring occasionally. Cut tofu into 8 equal pieces and drain well between paper towels. Place in a shallow dish and coat both sides with teriyaki sauce. Let marinate for at least 1 hour. Heat oil in a very large skillet over medium-high heat. Shake excess teriyaki sauce off tofu; add to skillet and cook for 2 minutes on each side or until nicely browned. Remove and let cool, then cut into strips. Place 1 tablespoon of mayonnaise on the bottom of each piece of bread. Top with tofu and pickled grape mixture. Add several sprigs of cilantro to each and close sandwiches. Serve immediately. Makes 6 servings.