Pour in the cranberries. Place the defrosted berries in a container and pour in vodka. Add sugar to taste. Close the lid tightly and place in a cool place where the drink will not be exposed to sunlight. Leave to infuse for 25 days. Shake the container every 5 days.
Strain the drink. After 25 days, strain the finished cranberry tincture through a sieve. Taste and add sugar if necessary. Leave to infuse for another 3 days in the refrigerator.