Make the ginger syrup: Combine 1/2 cup water, 1/2 cup sugar and the sliced ginger in a small saucepan and simmer for 10 minutes, until the sugar is dissolved. Remove the saucepan from the heat and stir in the vodka. Chill for 2 hours or overnight. When ready to serve, strain to remove the ginger pieces.
Spread the remaining 2 tablespoons sugar in a thin layer on a plate. Coat the rims of 8 glasses with the juice from the lemon wedges and immediately dip in the plate of sugar.
Add a few pieces of candied ginger to each glass. Pour 1 tablespoon of the ginger syrup over the ginger pieces and top with the sparkling wine.