Put the sugar and 250 ml water in a small saucepan and add the finely grated ginger. Heat everything until water vapor rises slightly, then let it draw covered for 5 minutes.
Meanwhile, chop the basil and 250 ml water in a blender for approx. 1 min. Maximum. Filter the ginger stock through a paper tea bag, add lemon juice and 1 liter of cold water.
Finally, filter the basil stock through a paper tea bag and add to the rest. Tastes best when chilled.
Another tip for all those who are calorie-conscious: Simply replace 50 g of sugar with the appropriate amount of sweetener.