For cinnamon curls, first dissolve yeast in milk, stir in sugar. Let stand until dough rises.
Put flour, salt, egg and butter in a large enough, sealable bowl, add yeast milk and applesauce and knead everything into a smooth dough.
Cover dough and let stand for an hour until well risen.
Knead dough together and divide into 16 portions (about 70 g each so that cooking time is the same for all donuts). Roll each portion of dough into a round, flat ball. Using a round cookie cutter, cut a hole in the ball.
Place on a baking sheet lined with parchment paper and let rise, covered, for another 20 minutes.
Heat the deep-frying fat to 175-180 °C.
Cut baking paper under the dough balls into pieces and, using the paper, place two pieces at a time “upside down” in the frying fat. Fry until golden brown on each side, then remove from the fat with a perforated scoop.
Drain the cinnamon rings briefly on a wire rack and roll in the cinnamon sugar.