Combine the vegan sugar and water in a large heavy saucepan and bring to the boil over moderate heat, stirring until vegan sugar dissolves. Turn heat up to high and cook briskly, uncovered, for 5 minutes, or until the syrup reaches 95C (200F) on a candy thermometer. Reduce heat to low, stir in remaining ingredients, and simmer for three minutes. Strain the sauce through a sieve. The ketjap will keep at room temperature for 2-3 months if tightly covered.