how to separate salt and sugar?

Sugar is organic (i. e it can be grown) and it contains carbon so to separate the sugar from the salt you need an organic solvent like alcohol (which is also made from organic materials, like live yeast and barley). Sugar and alcohol are organic, so sugar can dissolve in the alcohol.

Mixing the mixture of salt and sugar into alcohol will make the sugar dissolve into the alcohol leaving the salt behind, because it is organic, you can then filter this mixture of alcohol, sugar and salt to get the salt. Then to get the sugar all you need to do is evaporate the alcohol. Then you have your sugar and salt separate.