In a small bowl, whisk together ½ cup of the Cilantro Lime Dressing with the red wine vinegar and sugar. Place the haddock fillets in a zip lock bag, pour in the dressing mixture and coat the fish. Place in the refrigerator and allow to marinate for 15 minutes.
Meanwhile, remove the flesh from the mango and avocado, discarding the outer peel and pits. Dice into ¼” pieces and set aside.
In a small bowl, toss the red cabbage with the remaining ¼ cup of Cilantro Lime Dressing.
Heat a large non-stick skillet over medium heat. Remove the fish and discard the excess marinade. Place the fish in the pan and allow to sear for 3-4 minutes. Very gently, with a fish spatula, flip the fish over and sear the other side for an additional 2 minutes. Remove from heat and gently flake the fish apart.
At this point you can set up a build-your-own taco bar with the ingredients prepared, or you can assemble them yourself before serving. To do this, line up the tortillas on a flat surface. Divide the red cabbage mixture amongst the tops. Top the cabbage with fish and then with the diced avocado and mango and finally with fresh cilantro and a drizzle of Sriracha Aioli. Serve with a lime wedge.