27 CFR 6.91: Samples.

The act by an industry member of furnishing or giving a sample of distilled spirits, wine, or malt beverages to a retailer who has not purchased the brand from that industry member within the last 12 months does not constitute a means to induce within the meaning of section 105(b)(3) of the Act. For each retail establishment the industry member may give not more than 3 gallons of any brand of malt beverage, not more than 3 liters of any brand of wine, and not more than 3 liters of distilled spirits. If a particular product is not available in a size within the quantity limitations of this section, an industry member may furnish to a retailer the next larger size.