To Make the Cucumber Juice:

1. Wash and roughly chop the cucumber (peeling is optional).
2. Add cucumber pieces to a blender with a splash of water (1–2 tablespoons) to help it blend.
3. Blend until smooth.
4. Strain the mixture through a fine mesh sieve or cheesecloth into a bowl or measuring cup, pressing to extract as much liquid as possible. Discard the pulp.

To Make the Mint Simple Syrup:

1. Combine sugar and water in a small saucepan and bring to a simmer. Stir until the sugar dissolves, then remove from heat.
2. Add mint leaves and let steep for 15 minutes.
3. Strain and cool before using. Store in the fridge for up to 1 week.

To Make the Cucumber Cooler:

1. Fill a glass with ice.
2. Add cucumber juice, lemon juice, and mint simple syrup. Stir to combine.
3. Top with sparkling water and gently stir again.
4. Add your garnishes of choice and serve!