Place teriyaki marinade and 2 teaspoons of the chili sauce in a large recloseable food storage bag; stir to combine. Add steak, close bag and marinate 2 hours in refrigerator.
Stir together in medium bowl the syrup, vinegar, vegetable oil, sesame oil and 1 to 2 teaspoons of the remaining chili sauce. Add bean sprouts, red pepper, green onions and mint, if desired. Toss to combine; set aside.
Spray cold grill with grilling spray. Preheat grill to medium-high heat 20 minutes. Remove steaks from bag; discard bag with marinade. Cook steaks 8 minutes or to desired doneness, turning once or twice.
To serve, place each steak on a dinner plate and top with bean sprout salsa.