Yes it is right that you can separate by means of dissolving it to water, since sand is not water solouble and it will be easily segregated. However, if you will use water to filter it up IT IS IMPOSSIBLE FOR SUGAR TO BE BROUGHT BACK EVEN BY EVAPORATION as what some people believed above me. Sugar, once dissolve in water can only be seen via microscope. Because of water's polar bond, it becomes a great solvent for all substances, thus making sugar as its solute.. . So in conclusion, Yes you can separate it by the means of water, but I want to emphasize that the dissolution of sugar in H20 will cause irreversible result to which there would be no such process to bring it back again from its original form. . If you know any, let me know