Prepare the syrup. Pour a glass of boiling water into a saucepan, add sugar and boil, stirring. Bring to a boil and cook for about 2 minutes. The sugar should completely dissolve.
Chop the mint leaves with a knife or blender. Take a piece of gauze, pour the grated cucumbers and chopped mint into it. Squeeze the juice into a separate bowl or strain through a sieve with a spoon.
Add syrup, cooled water and lemon juice to the strained cucumber and mint juice. Stir.
Pour the lemonade into glasses.