Pour the vodka in to an air-tight bottle.
Chop up the lemons in to small pieces.
Place the lemon in the vodka, seal the bottle and leave for 3 weeks.
3 weeks later, filter the vodka either using a filter or a sieve and then pour the filtered vodka back in to the bottle.
Bring the water to the boil in a saucepan and then stir in the sugar.
When the sugar has melted, pour the sugar water in to the bottle and leave for another week. After a week, it's ready to drink.