Most brewery underwriters ask some version of the same question: How do you keep people who work around beer all day from driving after drinking it? A verbal answer rarely satisfies. A short written rule, signed by everyone who might drive a company vehicle or deliver in their own car, usually does.
Keep it specific to how a brewery actually works. Say that no one drives for the brewery after drinking anything, including a shift beer, a quality-control taste on the brewhouse floor or a sample poured at an account. Say what a driver does instead when an account manager insists on a pour: decline, or taste and spit if your sensory program needs it. Cover events, where staff who worked a pour shouldn't be the ones towing the draft trailer home. Then say what happens when the rule is broken, and apply it the first time.
Put the signed copies in each driver's file and send a blank copy with your application. It gets ahead of the underwriter's question, and it gives a manager something concrete to point to on a busy Friday.