Add cucumbers to the blender. Blend till pureed.
Press puree through a fine-mesh strainer into a medium bowl. Add cucumber juice, both vinegars, sugar and kosher salt to a jar or bottle. Shake very well to combine and refrigerate till cold.
Mix with water, sparkling water, sparkling wine or something like rum for a little extra kick. Typically you would use a 1:4 ratio when mixing a shrub mocktail/cocktail, however, taste as you go to find your preferred ratio.