The day before you plan to serve the pudding, line a mixing bowl with plastic wrap. Line the plastic wrap with the bread slices, trimming the pieces so that they fit together neatly. Save enough bread to cover the top of the pudding. In a saucepan, combine the apple juice concentrate and all the berries. Bring the mixture to a boil and cook until the strawberries begin to soften, about 1 minute. Immediately turn off the heat. Stirring, dissolve the gelatin in the water, then add the mixture to the berries and stir to combine. Spoon the mixture into the bread-lined bowl. Cover with remaining bread slices. Cover the bowl with plastic wrap and chill overnight. When ready to serve, whip the cream until soft peaks form. Remove the pudding from the refrigerator and remove the plastic wrap on top of the bowl. Carefully turn the pudding out onto a platter and serve in spoonfuls with whipped cream on top.