Preheat oven to 250°.
To prepare meringues, cover a large baking sheet with parchment paper. Draw 2 (8 x 12-inch) rectangles on paper. Turn paper over, and secure with masking tape.
Combine first 3 ingredients, stirring with a whisk. Place cream of tartar and egg whites in a large bowl, and beat with a mixer at high speed until foamy. Gradually add sugar mixture, 1 tablespoon at a time, beating until stiff peaks form (do not underbeat). Add vinegar and vanilla, and beat until combined. Divide egg white mixture evenly between drawn rectangles; spread the egg white mixture to the outside edges of each rectangle.
Bake at 250° for 2 hours or until dry. Turn oven off; partially open oven door. Cool meringues in oven 1 hour. Remove from oven. Carefully remove meringues from paper.
To prepare sandwiches, spread sorbet over flat side of 1 meringue; top with the remaining meringue, flat side down, pressing gently. Wrap sandwich tightly in plastic wrap; freeze 4 hours or until firm. Unwrap and cut sandwich in half lengthwise. Cut each half crosswise into 6 (2 x 4-inch) pieces. Cut each piece in half diagonally to form 24 triangles.