BBQ Mushroom Sandwich

Name: BBQ Mushroom Sandwich
Prep time: 5 min
Cook time: 13 min
Total time: 18 min
Cuisine: American
Ingredients: 1 tablespoon olive oil; 1 cup chopped onion; 1 clove garlic (minced); 8 ounces baby bella mushrooms ((3 cups sliced)); 1 tablespoon BBQ seasoning; Salt and pepper; 1/4 cup 4 ingredient sriracha BBQ sauce; 3 buns; 4 ingredient sriracha BBQ sauce ((optional)); Sliced pineapple ((optional)); Cilantro ((optional))