We know from How much sea water can I safely drink? that drinking salt water is not good. But adding any substance to water that will form a solute will lower the freezing temp. You can drink as much sugar water as you want, the only risk is added calories which you likely need anyhow.
The higher the concentration of salt, the lower the freezing point drops. Any foreign substance, such as sugar, alcohol, or any chemical salt, added to the water, forms a solute, which will lower the freezing point and melt ice. Source
So if I want to add sugar to my water to keep it from freezing how do I calculate how much sugar per unit of water I need to add, to keep it liquid at a given temperature?