Peel the bananas and slice lengthwise into 2 or 3 pieces. Skewer the slices together, or fry individually.
In a wide bowl, mix rice flour, baking powder, salt, and sugar. Add ½ cup water and vanilla. Whisk until smooth, then add more water until slightly thinner than pancake batter.
Heat enough oil to cover the bananas in a frying pan over medium-high heat. A small drop of batter should sizzle right away.
Dip the bananas in the batter. Let the excess drip off, then carefully lower into the oil. Fry in batches for 3–5 minutes per side, until golden and crisp.
Drain on a wire rack or paper towels. Sprinkle with sugar, if you like, and serve warm.
Notes
Saba bananas: Use ripe ones that hold their shape. Frozen saba, ripe plantains, burro, or Thai bananas also work.
Rice flour: Use regular, not glutinous rice flour. Cornstarch, potato starch, or all-purpose flour also work.
Baking powder: Helps make the coating crisp. Optional.
Sugar: Granulated or brown sugar works.
Oil: Use vegetable, canola, or peanut oil for frying.