Cut steak into one inch cubes. Cut the red onion into large chunks and set aside.
In a large bowl whisk together soy sauce, garlic, sesame oil, vegetable oil, sugar, ginger, and sweet sherry. Add the steak and toss to coat in marinade. Marinate for 3 hours or overnight.
Preheat the griddle to medium high heat. Thread the meat and the red onion onto the skewers. Grill for 8-10 minutes until the meat is done to desired liking.