In a medium saucepan over medium heat, combine shredded cucumber and water. Bring to a simmer and cook for 15 minutes, or until water has reduced by half.
Strain through a fine-mesh strainer over a bowl and discard the solids. Add sugar to the hot liquid. Stir until sugar has dissolved. Let cool completely.
Transfer to a glass jar and seal tightly with a lid. Store in the refrigerator for up to 1 month.
Notes
What cucumber to use? Any cucumber would work. I used 3 cocktail cucumbers, which is about the same as 1 large cucumber. Measure out the grated cucumber in cups for best results.