If it is a dry mixture, then you can use 100% alcohol which will dissolve the sugar, but not the salt (which can be filtered off). The alcohol has to be evaporated to yield the sugar.
If they are mixed in water, then you could try reducing the volume by boiling, but not too long in case, one or other comes out of solution. Addition of an excess of acetone to the solution should precipitate the salt, which can be filtered off. Evaporation of the acetone will yield the sugar. An alternative is to mix vigorously with toluene, which will dissolve the sugar but not the salt, and separate the layers using a separating funnel (as the toluene does not mix with water)
Water cannot be used to separate a mixture of sugar and salt as both sugar and salt show very good solubility in water. However, salt being an ionic compound would not be soluble in alcohol ( like dissolves like). On the other hand, sugar is very much soluble in alcohol. So on dissolving the mixture of sugar and salt in alcohol, the sugar would dissolve in alcohol, but salt would remain undissolved. The undissolved salt will settle at the bottom and can simply be separated by ltration. Now the solution of sugar and alcohol can simply be evaporated over a water bath (as alcohol is inammable) and the sugar can thus be separated from the alcohol solution