Corn sugar is a cheap fermentable sugar that produces alcohol without leaving the residual sweetness of malt extract. Corn Sugar, or dextrose, is used to prime your beer just before bottling so that the residual yeast is able to produce natural carbonation. Adding a small amount (no more than 10% of total fermentables) will increase alcohol content with minimal impact on taste. Corn sugar with use in quantities of 30-40% will produce a beer with a considerably lighter body opposed to stickily malt sugars. 4 lb bag.