Rim the edge of a chilled martini glass with water. Add the sugar to a bowl. Tilt the glass at a 45 degree angle and roll it in the sugar.
Fill a martini shaker with ice. Add the pear juice, vodka and lemon juice. Shake it to combine. Strain into sugar rimmed martini glass. Top with a splash of sparkling water and garnish with pear zest.
NOTES:
I have used unflavored Pellegrino and Pear Sparkling Water in this martini. Both are wonderful. The drink is a little less sweet with the unflavored water though.