Mash two of the cinnamon sticks with a wide knife. Then put the cinnamon, sugar and water in a saucepan. Bring the whole thing to the boil and let it cool in the pot.
Filter the resulting brew through a double-folded, clean tea towel. Put the remaining cinnamon sticks in a sealable glass vessel, add the filtered brew and fill up with the vodka.
Let the mixture stand in a dark place for about eight weeks, shaking occasionally. You will receive approx. 1 liter of finished schnapps.