History. Proficiency with brewer's supplies gives you additional insight on Intelligence (History) checks concerning events that involve alcohol as a significant element.
Medicine. This tool proficiency grants additional insight when you treat anyone suffering from alcohol poisoning or when you can use alcohol to dull pain.
Persuasion. A stiff drink can help soften the hardest heart. Your proficiency with brewer's supplies can help you ply someone with drink, giving them just enough alcohol to mellow their mood.
Potable Water. Your knowledge of brewing enables you to purify water that would otherwise be undrinkable. As part of a long rest, you can purify up to 6 gallons of water, or 1 gallon as part of a short rest.
Additional uses. You can use your brewer's supplies to do a variety of things, as your DM if you may use the tools for a specific task. Examples of such tasks are as follows; Detect poisons or impurities in a drink, identify alcohol, ignore the effects of alcohol.