 As gin was the predominant drink in the 1920s, many variations were created by mixing cheap grain alcohol with water and flavorings and other agents, such as juniper berry juice and glycerin.In addition, mixing grain alcohol, water, and flavorings in vessels large enough to supply commercial users had to be small enough for the operation to go undetected by the police.The common metal bathtub in use at the time would have been ideal as would have been a ceramic bathtub, hence the name, 'bathtub gin'.