Add soy sauce, oil, honey, apple cider vinegar, water, green onions, garlic, and fresh ginger to a large ziplock and seal. Massage to combine ingredients. Open bag and add cubed sirloin. Seal again and massage marinade into beef until it's all coated in marinade. Place bag on a dish and refrigerate for 4-6 hours.
30 mins before skewering steak, soak large wooden skewers in water for 30 mins. Remove and dry on a paper towel. Prep pepper and onion, if not already done.
Preheat grill to medium-high. Remove steak from fridge. Start skewer with a vegetable (onion or pepper) and then a piece of steak. Add the other vegetable and then another piece of steak. Repeat one more time so you have 4 pieces of steak on the skewer. Repeat until all the steak is used.
Cook skewers on preheated grill for 8-10 minutes, making sure to rotate so all sides get grill marks. Remove and sprinkle with sesame seeds, if using. Serve immediately.