There any many scopes from which we can see this question in order to answer it.
From the worker's point of view, the consumption of alcohol during or before their shifts can be prejudicial for worsening their reflexes, affecting their judgement as well as confusing their priorities and changing their temper. All of these can slow down their production, which will impact the production of the business.
From a boss' point of view, it can get in the way of relationships with business partners, suppliers, as well as the effects perceived by the regular worker. All of these would influence in the business production.