I suspect my company's salespeople are drinking during show hours. What's the best way to handle this situation when I'm at a show?
The best way to deal with this is before a show, not during one. Begin by documenting the incidents as best you can, and then meet with your supervisor and/or human-resources department. Explain the reasons behind your suspicions – offering your records as supporting proof – and develop a plan with their support for when you observe similar behavior at future shows.
Depending on what direction you receive, your next step likely will be to meet with all the salespeople. During your talk, explain that management is aware that some of them are drinking during exhibit-hall hours. Remind the crew that they are representatives of the company during the show and, as such, are expected to conduct themselves in an appropriate manner at all times. Let them know that any future occurrence of this misbehavior will be subject to penalties, such as dismissal from the trade show, and even being fired from the company.
If possible, give each salesperson a copy of your company policy that pertains to behavior during the show to further reinforce the message. To emphasize the gravity of the situation, remind them of the prohibition right before any show in an email and, if possible, in person. By taking a proactive approach for future shows, you should be able to help them stay sober instead of sloshed.