Cut the PVC piping in six 8 cm (3¼ inch) lengths.
Cut one sheet of acetate into six 11 × 8 cm (4¼ × 3¼ inch) rectangles. Cut the other sheet into six 4 cm (1½ inch) squares.
Melt the chocolate in a double boiler over simmering water. Spread evenly over the acetate rectangles to 1 mm (1/32 inch). Leave at room temperature to cool until almost set. Working with one at a time, and, using the acetate as a guide, curl the chocolate lengthways into a tube and place inside a length of piping, making sure it protrudes from both ends.
To seal one end of the chocolate tubes, spread the melted chocolate evenly over the acetate squares to 1 mm (1/32 inch) thick. Place a square at one end of the chocolate tubes, gently press to seal. Allow to set a little, then carefully peel away the acetate. Trim around the tube with a sharp knife to neaten.
Place in the freezer to quickly set, then fill the tubes with pineapple soup. Repeat the process to seal the other end of the tubes. Refrigerate until ready to serve.