Add mint to a cocktail shaker, Mason jar, water bottle, or anything with a lid and use a muddler or the back of a wooden spoon to muddle to release the flavour. Add lime juice an muddle a bit more.
Add the water, ice cubes, matcha, maple syrup, and alcohol (if using). Put lid on and shake vigorously to ombine.
Pour into a glass. Top it off with 2 ounces of sparkling water, garnishing with mint leaf. Serve immediately.