Whisk together the fresh lime juice, chili powder, and cumin until smooth. Set aside.
Prepare & cook the fish sticks according to the package directions. Brush them with the sauce.
When instructed to turn the fish sticks, do so and brush them again with the chili lime sauce. Stirring it if needed to incorporate again before brushing it on.
When the fish sticks are done cooking. Set them aside for five minutes to let them cool.
Assemble your tacos with lettuce on the bottom, then fish sticks, and finished with avocado pieces, tomatoes, and cilantro leaves.
Serve with sliced limes on the side to squeeze out over the tacos.