Hendrick's Gin is best, but any quality gin will do (Bombay or TanqTen are good options). This is a delicious and refreshing treat and I've been told a classic combination in the 20s.

Fill glass with ice (larger cubes are better) and two thin slices of cucumber.

Pour gin into glass.

Poor tonic water into glass.

Stir.

*don't pour too slowly, a fast pour will help release the cucumber's flavors.