Grab your cocktail rimmer (or small appetizer plates) and pour the granulated sugar in one, and the simple syrup in the other. Dip the rim of each martini glass into the simple syrup first, then dip into the granulated sugar. Set glasses aside.
Using your large shaker, fill it 1/4 full with ice and add the limoncello liqueur, vodka, whipped vodka, lemonade, and half and half. Close tight and shake well for 30 seconds.
Slowly strain the lemon martini mixture into the martini glasses. Pour it right in the middle and be careful to avoid the sugar rim. Garnish with a slice of lemon and serve.