Add vodka and stir well.
Fill glass 1/3 full with ice; squeeze lime slice over glass and drop into glass. Repeat until glass is full of ice and layered with lime.
Top off the glass with lime sparkling water or club soda and stir.
Garnish with fresh berries and a sprig of fresh mint before serving.
NOTE: For simple syrup, in a medium saucepan combine 1 cup sugar and 1 cup water. Bring to a boil, stirring, until sugar has dissolved. Allow to cool before using.