How do you stand out in a field of 20 Democrats striving to be president?

For Sen. Kirsten Gillibrand, the answer’s at the bottom of a beer-pong cup.

“Perks of being a young dem…. playing beer pong with @SenGillibrand and winnnning!” tweeted Shaye Weldon, who shared a photo of New York’s junior senator competing in a bar-top challenge. “This woman is a fierce passionate intelligent woman & an inspiration to young women everywhere.”

The picture suggested the 52-year-old Gillibrand hasn’t been partying too hard with college-age students in New Hampshire — the senator’s cups appeared to be filled with water.

Gillibrand’s stunt came after she posed with a drag queen in Des Moines, Iowa, earlier this month, part of her bid to boost her poll numbers from the 1 percent range.

Most of her rivals also pounded the pavement this weekend, trying to distinguish themselves from the 76-year-old Joe Biden.

Sen. Bernie Sanders, 77, tried to rouse his diehard supporters with thousands of hip-sounding house parties. Sanders and Biden are neck-and-neck in most polls.

The Vermont senator declared his candidacy two months ago — and raised more than $18 million in the first quarter, far more than any of his opponents.

So far, he’s devoted his efforts to rallies and other large-scale events, mostly in the early-voting states of Iowa and New Hampshire.

“At the end of the day, I believe now — and I’ve always believed — that grassroots activism is more important and more effective than 30-second television ads,” Sanders said.

Meanwhile, six Democratic candidates stormed a labor-union forum in Las Vegas, decrying low wages and what they described as corporate greed in order to win over the key voting block.

All of the Dems backed a $15 federal minimum wage.

“A minimum wage — that’s a minimum standard of living,” said Sen. Kamala Harris of California.

In response to a question about working conditions from a McDonald’s worker, Harris said she would press the burger giant’s CEO to pay better wages.

Sen. Elizabeth Warren of Massachusetts repeated her call for higher taxes on America’s 75,000 wealthiest families to pay for programs including free universal child care and student-debt relief.

She got the most applause.

“Let’s make the zillionaires pay a fair share,” she declared to cheers.

The event was organized by the Service Employees International Union, one of the country’s largest labor unions with 2 million members, and the Center for American Progress Action Fund, part of a Washington, DC-based liberal think tank.

Sen. Amy Klobuchar of Minnesota, former Colorado Gov. John Hickenlooper and former Obama housing chief Julian Castro also attended the event.

Former Congressman Beto O’Rourke of Texas said he would try to build support for conservatives while supporting unions.

“Unions are absolutely essential to the future of this country if we are to have a future in this country,” he said.

Biden, who jumped into the race on Thursday, was not there.

Still, he’ll likely tap into his longstanding union ties during the race.

With Wires