To determine the appropriate amount of sugar for a 30-gallon barrel of cracked corn mash, we need to consider the desired alcohol content, the fermentation potential of the corn, and the overall recipe's ratio. Generally, a fermentation potential estimate of 10-15% alcohol by volume (ABV) is common for cracked corn mashes. Taking this into account, a common ratio for a 30-gallon barrel of cracked corn mash is roughly 1.5-2 pounds of sugar per gallon of liquid. Therefore, for a 30-gallon barrel, you would need approximately 45-60 pounds of sugar. This range should provide a good starting point to achieve the desired alcohol content in your liquor.