Dextrose Corn Sugar - USE 3/4 cup per 5 gallons to carbonate beer. Dextrose corn sugar is an option for those who want to boost the corn-based fermentables in their wash without having to deal with the sticky, gluey mess of an all-grain corn mash. Each pound of dextrose corn sugar added will increase the ABV of a 5-gallon wash by about 1%. Adding a small amount of dextrose corn sugar (no more than 10% of total fermentables) will increase alcohol content with minimal impact on taste. However, a larger amount of the dextrose enzyme can be added, as well, for some spirit types (like Bourbon, which legally must be over 51% corn-based). It should be noted that using corn sugar dextrose is significantly easier than using corn grain but will not yield quite as much flavor.