Place the lavender in a large glass jar with a lid. Pour in the vodka and seal the jar. Let infuse 1 week, gently shaking the jar each day. Keep the jar in a dark place.
After a week, strain the vodka into a clean bottle.
In a saucepan, combine the sugar and water and boil until the sugar is just dissolved then let cool. Add to the vodka mixture and seal the bottle. Let rest in a dark place at least another week or two before drinking.