Vinegar
To make alcohol the key is to ferment it. But, if you ferment it a certain way, it will become vinegar.
Imagine making a bunch of vinegar. You use a key to change it from alcohol to vinegar, yum!
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You are demonstrating this practice in front of an audience. You want them to take you seriously so you wear a suit (す). A very nice suit. Surely they will now believe that you can turn alcohol into vinegar.
Imagine yourself doing the same thing as before but you are now wearing a suit. Dang, you look good.