Bring water, sugar, lemon juice, and allspice to a boil in a small saucepan over moderate heat, stirring until sugar is dissolved. Boil until reduced to about 1/4 cup. Remove allspice and stir in berries. Cook, tossing gently until berries are warm and juices begin releasing, about 3 to 4 minutes.
Serve over store-bought angel food cake and top with whipped cream.
Beat cream in a chilled bowl until frothy. Slowly beat in sugar and vanilla and continue beating until soft, glossy peaks form, scraping bowl often. Refrigerate until ready to use, then beat lightly with a whisk before serving.