Marinate steak: cut and trim the sirloin steak into 1" cubes. Place into a gallon-sized resealable plastic bag.
Mix the marinade by whisking together the vinegar, oil, Worcestershire, honey, garlic, garlic salt and pepper. Whisk well until the honey is well dissolved. Pour 1/2 cup of the marinate into a separate container, to reserve for brushing when the kabobs are grilling. Pour the rest of the marinade over the cubed steak into the plastic bag. Seal and refrigerate for 6 hours or up to 24 hours.
If using wooden skewers, soak the skewers in water for a minimum of 30 minutes before assembling the kabobs. Metal skewers do not need soaking.
When ready to assemble the kabobs, place cubed vegetables into bowls. Remove marinated steak from refrigerator. Alternate vegetables and steak pieces on the soaked skewers. Discard any remaining marinade that has been in contact with the raw meat.
Preheat outdoor grill or indoor grill pan to medium heat (outdoor grill, heat to approximately 375-400 degrees). Place skewers on the hot grill grates, rotating/turning the kabobs every 2-3 minutes. Brush the skewers with the reserved marinade when turning the kabobs. Cook for 8-10 minutes total for medium doneness.
Let rest for 5-10 minutes before serving.