Put a little simply syrup around the rim of two tall glasses.
Dip the glasses into the graham cracker crumbs to rim the glasses.
Fill the glasses with ice.
In a shaker combine the simply syrup, key lime juice, and vanilla vodka. Shake well and pour over top of the ice in the glasses, filling about halfway full.
Tear the mint leaves and place them into the glasses.
Top the glasses with soda water.
Stir with a straw and enjoy!