In a medium bowl, whisk together the flour, baking powder, and salt.
Gradually whisk in the cold beer until the batter is smooth and has the consistency of pancake batter; let it rest for 10 minutes.
Prepare the crema by mixing the Mexican crema, mayonnaise, lime juice, and hot sauce in a small bowl; set aside.
Heat vegetable oil in a heavy-bottomed pot or deep skillet to 375°F (190°C).
Pat the fish strips completely dry with paper towels to ensure batter adhesion.
Dip fish strips into the batter one at a time, allowing excess to drip off, and carefully lower into the hot oil.
Fry fish in batches for 3 to 4 minutes, turning once, until the coating is golden brown and crispy.
Transfer fried fish to a wire rack or paper-towel-lined plate to drain.
Warm the corn tortillas on a dry skillet or over an open flame until pliable.
Assemble tacos by placing one piece of fish on a tortilla, topping with shredded cabbage, cilantro, a drizzle of crema, and a squeeze of lime.