Preheat the oven to 180 ° C (convection). Peel the apple and cut into small pieces.
Mix the egg lightly until frothy, then add 140 g sugar. Sieve 230 g flour, baking powder, baking soda and cinnamon. Mix 80 ml of oil and 200 ml of apple juice. Stir in the flour mixture and the oil-apple juice mixture alternately. Slowly fold in the apple pieces.
Pour the batter into the muffin pan and bake for about 20-25 minutes.