When substituting sweet vermouth for a cocktail, such as a Manhattan, port is an acceptable substitute. For use in a recipe, many liquids can take the place of vermouth, such as grape juice or apple juice.
Another acceptable substitution for sweet vermouth in a cocktail is Madeira wine. Any cocktail substitution can be used for cooking as well. However, many substitute items in place of vermouth to remove alcohol from a recipe. Other non-alcoholic sweet vermouth substitutes include water in lemon juice, balsamic vinaigrette and non-alcoholic sweet wine. A good substitute for dry vermouth is white grape juice or white wine vinegar.