Slice the bananas into very thin rounds about 1/16 inch thick using a mandoline for even results.
If using the soak, place the slices in water with lemon juice for 5 to 10 minutes, then drain and dry them completely so no moisture remains.
Heat the oil in a heavy pot to 325–335°F.
Fry the banana slices in small batches for 4 to 6 minutes, stirring occasionally to ensure even cooking.
Continue frying until the bubbling becomes small and quiet, the chips turn light golden, and the slices feel firm and crisp when lifted from the oil.
Transfer the chips to a wire rack to drain and allow excess oil to drip off.
While the chips are still hot, place them into a mixing bowl.
In a separate bowl, combine the granulated sugar, cinnamon, and salt until evenly mixed.
Sprinkle the cinnamon sugar over the hot chips and gently toss until all pieces are evenly coated.
Spread the chips out in a single layer and allow them to cool completely until fully crisp.