Preheat the oven to 400. Line a baking sheet with foil or parchment. Place the fish fillets on the baking sheet and drizzle with the olive oil.
In a small bowl, whisk together the garlic powder, cumin, chili powder, salt, and pepper. Sprinkle the spice mixture over the fish and rub to coat.
Bake 20-25 minutes, or until the fish is opaque and flakes easily.
While the fish is baking, whisk together the sour cream, mayonnaise, sriracha, and lime juice. Refrigerate until ready to serve.
To assemble the tacos, break the fish into smaller pieces using a fork. Stack two tortillas together, and place 1/2 of a fish fillet onto each stack. Top with cabbage, tomato, and cotija, and drizzle with the taco sauce. Squeeze fresh lime over the top, and enjoy.