Make the marinade: In a bowl, combine the vinegar, olive oil, sea salt, and red pepper flakes.
Cut the mushrooms in half, add to the marinade and toss to coat. Let sit for 30 minutes.
Slide the mushrooms onto metal skewers or bamboo skewers that have been soaked in water during the marinating time.
Heat your Spark to 500°F and oil your grates. Cook the skewers for about 3 minutes, then flip and cook for another 3 minutes.
Remove the skewers from the grill and serve along with your main course.