In a large bowl, stir together the vodka, two-thirds of the sliced strawberries and the granulated sugar. Cover with plastic wrap and let stand at room temperature until the vodka turns pink, about 6 hours. Refrigerate overnight or up to 3 days.
Strain the vodka and divide among 6 tall glasses. Add a splash of limoncello to each glass and top off with the sparkling wine. Drop in a sugar cube and garnish with the remaining strawberry slices.