Place chicken breasts in your slow cooker.
In a mixing bowl combine barbecue sauce, brown sugar, tequila, Italian dressing and hot sauce. Stir until combined. Pour the sauce over chicken. Cover and cook 5 hours on LOW or 3 hours on HIGH. Remove chicken from slow cooker.
Shred chicken using 2 forks. Return chicken to slow cooker; mix and heat with sauce before serving.
For the Nachos:
Preheat oven to 400°F. Line a rimmed sheet pan with parchment paper and spray generously with non-stick cooking spray.
Spread tortilla chips in a single layer on the prepared sheet pan. Sprinkle with 1 cup of cheese, corn, fresh salsa, green onions, and shredded tequila barbecue chicken. Then sprinkle the the rest of the cheese all over the toppings.
Bake nachos for 10-15 minutes, or until cheese is melted. Remove from oven.
Garnish with cilantro leaves. Serve with guacamole and/or sour cream, if desired.