Bring water and sugar to a simmer on medium heat, stir until sugar is dissolved.
Turn heat to medium-low and add the lavender sprigs; simmer for 1-4 minutes (depending on how strong you'd like the lavender flavor).
Turn the heat off. Let the syrup steep for at least 30 minutes, but for stronger flavor allow to steep until completely cool.
Once steeping is done, strain the simple syrup through a fine mesh strainer into a glass jar. If not completely cool, allow to cool before using or putting in the fridge.
Making the drink:
Place the basil and mint in a rocks glass, and using a muddler (or the end of a wooden spoon), crush the leaves to release the basil and mint oils.
Add the lemon juice, 1/2 oz. of lavender simple syrup and the gin; stir to combine (if you like a sweeter drink add in the additional 1/4 oz. of lavender simple syrup).
Fill glass with ice, and top off with sparkling water. Garnish with lavender sprig and/or lemon wedge. Enjoy!