Wash and pat dry the sloes.
Prick the sloes with a toothpick. This process can be omitted if you have picked the sloes after the first frost or you have frozen them in your freezer (causing the skins to split)
Pack the sloes into the bottle.
Add the sugar on top of the sloes.
Pour in the gin. Leave a bit of space on the top as it will increase in volume a bit as the juice from the sloes is released.
Close the lid. Label the bottle and store in a cool dark place for about three months. For the first week shake the bottle everyday to distribute the sugar.
After three months or so, strain the gin using a fine mesh sieve lined with a muslin cloth.
Decant back into the gin bottle. Seal and label.
With the passage of time, the sloe gin will mature even more. Enjoy.