Core and peel the apples and cut each into 4 thick slices. Put them in a shallow dish with the sugar and brandy, rum, or liqueur, and turn them so that they are well coated. Leave for at least 1 hour, turning the slices over occasionally so that they absorb the spirit.
For the batter, beat the yolks with the oil and salt, then stir in the flour and mix well. Now beat in the water gradually and vigorously, squashing any lumps. Leave for an hour, then fold in the stiffly beaten egg whites.
Heat at least 3/4 inch of oil in a large frying pan. Dip the apple slices in the batter about 5 at a time-making sure that they are well covered with batter. Lift each one out carefully and lower into the hot oil. The oil must be sizzling but not too hot, or the fritters will brown before the apple is soft inside. Fry in batches, and turn the slices over to brown both sides. Lift out with a slotted spatula and drain on paper towels before serving. Pass the superfine sugar for everyone to sprinkle on.
Recipe courtesy of Claudia Roden, "The Book of Jewish Food"