Whisk liquid smoke, maple syrup, and salt in a large, shallow bowl.
Place mushroom strips in the liquid smoke mixture, making sure all mushrooms are entirely covered, and marinate for 15 minutes.
Heat oil in a large skillet over medium-high heat. Cook the mushrooms for about 3 minutes, then flip and cook for 3 more minutes. They should be browned and the edges should look crispy.
Assemble each sandwich evenly with the bread, bacon, tomatoes, lettuce, and mayo.