by Rabbi Yitzchak Hanoka, Kosher Spirit
First, we have to look at the question from a halachic perspective. Is cold liquid in a non-kosher vessel permissible? The simple answer is that one is allowed to use a clean non-kosher vessel for cold liquids on a temporary basis, as long as one does not have the liquid sitting in the vessel for 24 hours (the time it takes for kovush – pickling).
Halacha requires all non-kosher vessels to be cleaned before use. One can rely on the fact that a reputable establishment keeps all items clean to comply with health regulations.
To explain further, regular liquids have a 24-hour time period of before kovush and absorbing from the vessel in which it is contained. Sharp liquids, like alcohol, would absorb in a shorter period of time (18 minutes). This is only true if the majority of liquid is alcohol, but most alcohols are not considered sharp liquids, because they would have to be over 100-proof (more than 50% alcohol).
The average alcohol contains a substantial amount of water and is not pure alcohol. In addition, many mixed drinks, like Bloody Mary, Screwdriver, etc. are even further diluted. With mixed drinks, it is imperative to make sure that each ingredient is kosher certified.
When drinking a shot, most people drink it right away, within 18 minutes and in most cases, the shot is not strong enough to absorb in 18 minutes anyway.
In a case where someone is drinking a “sharp” alcohol, like Zektz un Ninetzinger, it is proper to make sure to drink it in less than 18 minutes. Some Sefardim hold of the Beis Yosef’s opinion that glass does not absorb at all and are lenient, but the minhag of Ashkenazim is to be machmir.
A slice of lemon or lime (commonly added to drinks) is a sharp food cut with a non-kosher knife and is not permissible.
There is also a din of not drinking with goyim at non-Jewish parties (like an office holiday party).
This response was written for situations when one is socializing in a Torah-permissible manner (i.e. Shidduchim, etc.). For questions regarding a non-Jewish party, please ask your local Orthodox rabbi.