The Empty Booze Barrel is used to Brew drinks such as Beer and Rum. To be used, it has to be placed onto a wooden Scaffold and then have Water Cells, Hops and Wheat or Sugar Cane placed inside by holding them in your hand and right-clicking the Empty Booze Barrel. Fermentation will then begin and the outcome will depend on the ratio of the ingredients and how long they've been brewing.
Using a Treetap on the barrel will stop the fermentation and allow you to fill up Stone Mugs. Fermentation will continue after the tree tap is knocked off by left clicking the barrel. It can only be crafted with rubber wood, not spruce wood, jungle wood, Rubber Tree (RedPower2), or pine wood.