Open containers as in alcohol? Never. If I even suspect it's alcohol then no. Absolutely no liquids of any kind during drunk hours. Daytime I may allow a fountain soda with lid or coffee with lid if they ask. Anything with no lid forget it.
If they protest at all I cancel. Usually I kick them out and wait what's left of 5 mins and cancel. I'll argue with them a minute or two just to run the clock down.