Add the sloes, sugar and gin. Seal the cork/cap/lid and swirl the contents together for 30 seconds or so. Set aside in a cool, dry, dark spot
Each day for about a week, swirl the contents together for 10 seconds or so. Once all the sugar has completely dissolved, you can strain to remove the fruit and store the sloe gin (for years... if you can resist the urge to crack it open!)