Place English Cucumber (1/2) in a small pitcher or jam jar. Mash with a muddling tool or a wooden spoon until cucumbers release juices. Add Gin (2 cup), cover, and refrigerate at least 12 hours and up to 3 days.
Add Granulated Sugar (250 gram), Water (250 milliliter), Peppercorns (5) into a heavy-based saucepan. Over a medium heat allow the sugar to dissolve into the water.
Once the sugar has dissolved, bring the liquid to the boil and boil for 5 minutes. Remove from the heat and set aside to cool.
Juice the Grapefruit (3/4 cup).
To assemble, place Ice (1 handful) into glasses, add 1–2 shots of gin (depending on how strong you like it), 1 tablespoon of syrup, grapefruit juice, and top with Carbonated Water (1/3 cup).