Mix the mayonnaise, Sriracha, lime juice, sugar, 1/4 cup cilantro and 1 tablespoon water in a large bowl. Toss with the coleslaw mix, mango, and red onion. Season with salt and pepper and set in the refrigerator until ready to serve.
In a bowl whisk together the flour and baking powder. Whisk in 1 cup seltzer until smooth and let batter stand for 10 minutes.
Heat oil in a heavy-bottomed pan over medium-high heat until it reaches 350 degrees.
Season fish with salt and pepper. Working in batches, dip each fish piece in the batter, transfer quickly to the hot oil and cook until golden brown, approximately 2 minutes. Transfer to a paper lined plate to drain before serving. Season again lightly with salt on both sides.
Assemble your sliders with the fried fish pieces and top with coleslaw. If you like extra sauce on your sliders (I always do!), add some Sriracha mayonnaise spread on the bottom bun of each slider before topping with the fish and coleslaw. To whip up a quick Sriracha mayonnaise, combine a 1/4 cup mayonnaise with 1 to 2 tsp Sriracha (add more if you want more spice!).