Place cut steak in a large gallon-size resealable bag.
In a mixing bowl, whisk together soy sauce, garlic, ginger, vegetable oil, sesame oil, Truvia and Diet Coke. Pour mixture over steak in bag, seal and let marinate for at least 3 hours, or overnight.
If using bamboo skewers, soak in water for at least 20 minutes before grilling to avoid burning. Preheat a grill to medium- high heat.
Thread steak onto skewers, grill for 8-10 minutes, turning throughout cooking until steak reaches desired doneness. Garnish with sesame seeds and green onion.