Divide 1 bottle of Mountain Dew, and 1 bottle of Powerade Mountain Berry Blast Sports Drink into 4 gallon-sized zip-top bags. Remove as much air as possible from bags and seal bags carefully (or double bag). You will end up with 4 bags. On a rimmed baking sheet freeze bags until solid, 2 to 3 hours.
One at a time, working quickly, wrap each bag with a kitchen towel; using a rolling pin or a kitchen mallet, tap bag all over until soda is broken into chunks small enough to fit into a blender.
In blender, in two batches, combine 1/2 bottle of Mountain Dew and 2 bags of frozen soda. Blend until smooth and slushy. Serve immediately.