On a lightly floured surface, gently unroll second pie crust. Cut it into 3/4 in. strips. Place strips horizontally, then weaving in vertically, across the top of the pie, trimming so that each strip comes to the edge of the pie. Fold bottom crust over strips and crimp. Whisk together egg with water until well combined. Brush over strips and edges of pie. Sprinkle with sparkling sugar, if using.