2 cups cold water
4 envelopes unflavored gelatin
1-1/2 cups sugar
2 bottles (750 milliliters each) Champagne or sparkling grape juice
2 cups sparkling grape juice
3 cups fresh raspberries
3 cups fresh blueberries
2 cups fresh blackberries
Place water in a large saucepan; sprinkle with gelatin. Let stand for 2 minutes. Add sugar. Cook and stir over medium-low heat until sugar and gelatin are dissolved (do not boil). Remove from the heat.
Measure 4 cups Champagne; set aside remaining Champagne and chill for another use. Slowly stir the 4 cups Champagne and 2 cups grape juice into the saucepan.
Transfer to a 13-in. x 9-in. dish coated with cooking spray. Cover and refrigerate for 8 hours or overnight.
Using a potato masher, gently break up Champagne jelly. Layer the jelly and berries in 12 dessert dishes. Cover and refrigerate for at least 2 hours before serving.