HOJE-TAASTRUP, Denmark—Michael Christiansen, a truck driver turned union representative, is fighting hard to preserve one of the last, best perks of the beer industry: the right to drink on the job.

Mr. Christiansen’s union brethren are wort boilers, bottlers, packers and drivers at Carlsberg A/S, Denmark’s largest brewer. For a century, they’ve had the right to cool off during a hard day’s work with a crisp lager.

But on April 1, the refrigerators were idled and daily beer spoils were capped at three pint-sized plastic cups from a dining hall during lunch hour.