When Julie McCarthy was a college student, she learned a time-honored budgeting tactic: Downing vodka in her dorm room with friends meant spending less later at the club.

Now 31, she’s dusting off the strategy to combat rising prices for drinks at concerts and raves. On one recent night out, a Massachusetts concert venue was charging $20 for a tall-can of black cherry White Claw.

“I saw that and thought ‘Wow, I’m really glad I pregamed’,” said McCarthy.

With prices for everything from groceries to gas climbing , Americans are pinching pennies and making hard choices. Many have cut out alcohol altogether. For those who still crave a cocktail, they’re entering a flashback era of “pregaming,” downing a few drinks at home before going out to keep from spending much more to get the same buzz.

Nearly a third of the 1,000 people surveyed by Zappi who had drinks within the last three months said they now predrink to avoid paying higher prices at venues. Drinkers are trading tips on how to sneak alcohol into events, often gravitating toward the miniature-sized bottles sold by many alcohol makers.

Suntory Global Spirits is seeing higher demand for its nips of Jim Beam and Maker’s Mark, said Chief Executive Greg Hughes.

“You’re seeing consumers gathering at home or a friend’s house before going out,” said Hughes. “They’re trying to stretch the dollar by pregaming. You can see that’s what’s growing.”

The average price of a cocktail in America is now $13.61, according to market-research firm Technomic. In places like New York City, it’s much higher.

Manhattanite Alexis Candee said with those prices, she can make four drinks for the price of one cocktail. On a recent Tuesday night, a martini at home before going out to see “MJ the Musical” kept her from splurging $36 on a vodka soda.

Drinkers are trading tips online about how to sneak alcohol into events and ways to pregame. Elizabeth Coetzee/WSJ

These days, her friends have even taken to “post-gaming,” stopping by her apartment after the bar for a nightcap. It’s the difference between opening a costly tab at yet another bar or mixing their own drinks for free at her place.

“In my 20s affordability was really the name of the game,” she said. “But that’s still the case now in my 40s.”

Reddit forums are full of advice on how to hide nips under clothes and within bags to evade security and make it into concerts, like the Backstreet Boys at the Sphere. Those in Las Vegas are offering tips on convenience and liquor stores with the lowest prices, so that Strip-goers can catch a buzz on the cheap. Open-container laws help keep the party going on the Strip.

Flasks are becoming more common, and not just in Sin City. Pregamers are also sipping whiskey on the couch before grabbing a cab for a night out. And a glass or two of wine before a dinner reservation has allowed some to keep dining out, even with rising food costs.

Big brands are getting in on the action, too, selling smaller bottles to strapped U.S. consumers as a way to enjoy—or discover—their tipples at a lower price.

Diageo put its premium Don Julio 1942 extra Añejo tequila into 50 mL containers. Angel’s Envy will soon sell 50 mL bottles of one of its whiskeys. Last year Kendall Jenner’s 818 Tequila brand debuted its own airplane-sized bottles—designed as a fashion accessory and a way to drink tequila on the go. At ALB Vodka, sales of airplane-sized bottles in the first quarter more than tripled, compared with the same period last year. The 50 mL size significantly outsold larger sizes.

Comedian and actor Jim Gaffigan, speaking on the way to a comedy gig in New York, said he figured people were pregaming for his show given the high price of alcohol. He did the same in his 20s.

“In college, that’s where you learn it,” said Gaffigan, who co-founded the Fathertime bourbon brand. “If we are going to get a buzz on, we aren’t going to go to the bar and start the journey. It’s financially sound advice.”

Among drinkers who say higher prices influence their decision to go out, Zappi, a consumer-insights platform, found that 41% have switched to water or nonalcoholic options, while 37% predrank to avoid paying venue prices.

That’s exactly what led McCarthy and her husband to gather with a group of friends on the grass before a recent AJR concert in Mansfield, Mass. They set out a picnic blanket and brought a cooler stuffed with White Claw seltzers and Sam Adams beers.

After having some drinks, they put the cooler back into the car. “Then it was a bit of a walk to go into security,” she said. There’s an art, McCarthy added, to drinking just enough to have a buzz but not be intoxicated — so you can still be admitted to the venue.

She still bought alcohol inside, she said. But far less than she would have, had she not pregamed.

“I spent almost as much on the concert ticket as I did on booze,” she said. “I spent so much on alcohol I didn’t want to spend another $20 on a hot dog. We just ate popcorn.”