BOSTON—A battle is brewing in Massachusetts between state regulators and Anheuser-Busch InBev NV over allegations the beer giant has provided nearly $1 million in unlawful giveaways to entice retailers and bars to push Budweiser over rivals.

The state’s Alcoholic Beverages Control Commission has issued a report detailing investigators’ findings and set a June hearing in Boston on the matter. The report alleges a subsidiary of AB InBev gave out bar equipment as incentives to hundreds of Massachusetts businesses in violation...