In a medium bowl, mix together the flour, baking powder and salt. Pour in the bubbly water, starting with about 3/4 cups and adding more as needed, to achieve a consistency a little thicker than pancake batter.
Heat the oil to 350°F - 375°F.
Using tongs, coat a piece of chicken in the batter, letting the excess drip off.
Carefully lower the battered chicken piece in the hot oil.
Let cook about 2-3 minutes per side, or until golden brown and chicken is cooked through. Repeat in batches for the remaining chicken.
Place the cooked pieces on a baking rack to let the excess oil drain off.
Place the cooked chicken in a large bowl and cover with the BBQ sauce. Toss to coat.
Notes
You'll likely need to fry the chicken in batches. I fry mine in a large cast iron Dutch oven and fry in three batches.