Buy a $30 pint glass, get a free beer at participating Austin breweries — that's the simple premise of Barks for Beers. It has proved irresistible for the thousands of locals who have helped to raise money over the course of five years for Divine Canines.

Barks for Beers organizer Mike Pizinger thinks it's not just the philanthropic aspect of the event, returning this weekend through May 31, that has made it so popular. (But, of course, there's nothing sweeter than helping therapy dogs bring people joy.) Each year, the list of Austin-area breweries participating in Barks for Beers changes as new ones open and previous participants take a year or two off.

The ever-rotating list means that there's probably somewhere new for brewery lovers to check out with a free pint.

"We like switching up the breweries that participate every year," Mike Pizinger said. "What we regularly hear from people is that (Barks for Beers) encourages them to go to places they've never been before."

This year, Barks for Beers breweries include North Austin's Circle Brewing, South Austin's Skull Mechanix Brewing and Dripping Springs' Family Business Beer Co. — 22 in total, spanning a wide swath of Austin and the surrounding Hill Country. Many of them are grouped close enough that it's easy to turn a weekend afternoon into a mini brewery crawl, which is something, he said, that Barks for Beers' more than 5,000 yearly participants like to do.

Not all of the breweries are near each other for a quick drive. Two Wheel Brewing, for example, is in Buda, and Infamous Brewing is in the Lake Travis area. But there's an incentive for you to complete the "pawsport" that comes with each Barks for Beers pint glass, marking where you've been. Visit each of the 22 breweries, and each pint amounts to roughly $1.36. Not a bad deal, huh?

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Not sure when to head to each one? Generally, each brewery will have at least one Barks for Beers party starting April 26, and though you can get your free pour with the pawsport at any time during taproom hours, the parties will have freebies, raffles, games and, of course, adorable Divine Canines therapy dogs in attendance. To keep up with the full schedule, head to Divine Canines' Facebook event page.

Proceeds from the sale of the glasses go directly to the therapy dog organization, which as a result of the popular fundraiser was able to train 45 new dog-and-handler teams in the past year. Divine Canines spreads joy and tranquility to almost 200 sites around Austin that include assisted living facilities, inpatient rehabilitation facilities and elementary schools.

For more information, visit divinescanines.org/barksforbeers.