Heat the applesauce in a saucepan over low heat, stirring constantly, until heated through, about 5 minutes. Off the heat, add the raspberry gelatin and stir until dissolved. Add the raspberries, along with any juices remaining in bag, and the soda. Pour into a 2-quart bowl, cover and refrigerate overnight.
Just before serving, use an electric mixer fitted with a whisk attachment to whip the cream until it begins to thicken, 3 to 4 minutes. Add the vanilla and continue to whip until firm. Spread the whipped cream over top of the gelatin. Serve cold.