A trip to the bathroom is usually the result of a medical condition that I'm sure they wish they didn't have to deal with, either.  I used to have a few clients that would need to take a smoking break, about 15 minutes into an appointment.  When they returned, I was too meek to ask them not to exhale.  I lost a couple clients when I started out, many decades ago, because I wouldn't allow smoking in my office.  (Most people refrained when I told them it was bad for the computer.)  

It's usually the women, but sometimes the men who use way too much cologne or after-shave.  I just keep the air recirculating, and give thanks that I haven't lost my sense of smell to dementia or lately, Covid.

I accept food for later consumption.  My 90-year-old client brought me the usual banana bread with chocolate chips and maraschino cherries.  And the guy who sold the vineyard -- he brought us two bottles of wine today anyway, made from "his" grapes.