Combine sugar, soy sauce, sriracha, lime juice, sesame oil and garlic in a shallow dish. Add steak, cover and marinate for 1 hour; turn after 30 minutes.
While steak is marinating combine sauerkraut and fresh cabbage together and set aside.
Preheat grill to medium-high. Remove steak and discard marinade. Thread steak onto skewers; sprinkle with salt. Place skewers on grill and cook 3 minutes on each side or until desired degree of doneness. Remove, cover and set aside.
Grill tortillas 30 seconds on each side or until lightly charred; keep warm.Place 2 tortillas per plate, and divide steak evenly among tortillas. Top each taco with cabbage mixture; sprinkle with onions, top with Sambal Matah and serve.