If you put any significant amount of copper in water with oxygen present the copper will oxidize and you are going to be left with a green mess. Bicardi 151 is 75% alcohol and will sterilize most anything. Everclear is 95% and would be the better choice. Most gins are 40% alcohol and have quite a few added spices to flavor the gin. I would be concerned about whether the gin would change the taste of your cigars. All that being said if you use distilled water and check your humidifying system regularly you should not get mold. Just my
.