Step 1

For lemon-myrtle syrup, bring 250ml water to the boil, add lemon myrtle, then remove from heat and leave to infuse, stirring occasionally, for 10 minutes. Strain (discard leaves), then add sugar and stir to combine. Cool, then transfer to a bottle and refrigerate until required.

Step 2

For 1 serve, combine 40ml syrup and 1 tsp vinegar in a tall Collins glass, and stir to combine. Fill glass with ice, top with soda water and garnish with cucumber and mint to serve.