When fermenting for high alcohol the main ingredients are sugars and yeast.
Generally you will want your sugar wash to be neutral tasting, so that you can flavour it with essences or ingredients later. This makes plain dextrose sugar or syrup an ideal source. Not only is it inexpensive to use in large quantities, it also creates a clear flavour neutral wash when fermented.
Alternatively, you could use grains in your wash as well. Grains are not as efficient as a source of sugar, but they can add specific flavours to your wash.
The ABV strength of your wash will depend not only on how much sugar you use, but also on whether or not the yeast you use is strong enough to ferment in a high alcohol environment. Specially formulated yeast products like Lightning Turbo Yeast are packed full of a strong yeast and nutrients to keep it going up to 23% in just plain sugar water. There are also specialized yeasts for whiskey, vodka, or rum style washes that are recommended if you are using additional sugar ingredients like grains or cane sugar.