Heat a large skillet over medium heat. Pat the shrimp completely dry with paper towels. In a bowl, whisk together the sugar, paprika, chili powder and onion powder. Sprinkle it evenly over the shrimp. Add the butter to the skillet. Once it’s sizzling, add in the shrimp and cook on both sides until pink. You can do this in batches if needed – you don’t want to overcrowd the pan. The butter will brown as the shrimp cooks and you can whisk it occasionally to prevent it from burning. When the shrimp is finished, stir in the garlic and BBQ sauce. Turn off the heat.
In a bowl, mash the avocados with the salt, pepper and lime juice. Smash the avocado on the toast pieces evenly. Top the avocado with the shrimp. Sprinkle some of the queso fresco on the shrimp and cover with the herbs. Eat up!