Mix the sugar and cinnamon. Unroll the puff pastry and sprinkle with the sugar and cinnamon mixture. Roll up the puff pastry on the long side. Now cut about 1 cm thick slices from the roll and place on a baking sheet lined with baking paper.
Bake at 180 degrees for about 15-20 minutes.
Make a frosting from powdered sugar and water and coat the cooled cinnamon buns with it.