
Rinse the green shiso leaves thoroughly under cold water to remove dirt or debris.
Gently pat them dry with paper towels or shake off excess water.
In a medium-sized saucepan, bring 250 ml of water to a boil.
Boil the leaves for about 5 minutes until the water turns a light green and the leaves wilt.
Remove the pot from heat.
Strain the liquid through a fine mesh sieve into a clean bowl or pot.
While the liquid is still hot, stir in the sugar until fully dissolved.
Once it has cooled down a bit, stir in apple cider vinegar or lemon juice.
Let the juice cool to room temperature.
Pour into a clean, sterilized bottle or jar.
Store in the refrigerator for up to 1–2 weeks.
Fill glasses with ice cubes.
Pour 1 part green shiso juice over the ice and dilute with 3 parts soda water or cold water.
Garnish with a fresh shiso leaf, or mint, or a slice of lemon or lime, if you want.