‘Tis the season to mix milk into your soda. According to Pepsi, anyway. Pepsi launched a campaign Thursday encouraging customers to try the combination and use the hashtag #PilkandCookies (as in Pepsi plus milk) to showcase their Santa-friendly concoctions. Those who participate in the online challenge running through Christmas Day will have the chance to win cash. “Combining Pepsi and milk has long been a secret hack among Pepsi fans,” said Todd Kaplan, Pepsi’s chief marketing officer, in a statement about the campaign. Pepsi is now publicizing the mix as its spin on “dirty soda,” a popular TikTok trend that combines soda with syrup and cream. Companies like PepsiCo\n \n (PEP) pay attention to what’s happening on TikTok, and often look for ways to get in on trends as a way to stay relevant to young consumers. “With the rise of the ‘dirty soda’ trend on TikTok and throughout the country, we thought Pilk and Cookies would be a great way to unapologetically celebrate the holidays,” said Kaplan. To make the campaign even trendier, Pepsi tapped Lindsay Lohan, star of the Netflix\n \n (NFLX) Christmas movie “Falling for Christmas,” to promote the combination. Pepsi is recommending a number of recipes to those who want to go beyond just Pepsi and milk, perhaps hoping to launch its own viral combination. A handful of those recipes include the Naughty & Ice, which is Pepsi with one cup of whole milk, one tablespoon of heavy cream and one tablespoon of vanilla cream, plus Pepsi; the Cherry on Top combines Pepsi Wild Cherry with half a cup of 2% milk, two tablespoons of heavy cream and two tablespoons of caramel creamer; and the Snow Fl(oat) is Pepsi Zero Sugar and half a cup of oat milk with four tablespoons of caramel creamer. TikTok trends The soda cocktails are relatively new to TikTok — but they have been popular for years in Utah, which has a high concentration of Mormons, some of whom abstain from alcohol and hot beverages. TikTok discovered the drink after Gen-Z pop star Olivia Rodrigo posted a photo of herself holding a Swig cup in December last year, sending fans in search of answers about the Utah-based chain. Swig, which calls itself “home of the original dirty soda,” has been around since 2010 and serves a wide array of the carbonated mash-ups. The trend quickly took off, Eater reported in April, saying “TikTok is now replete with more than 700,000 mentions of the #dirtysoda hashtag, most of which accompany videos of creators showing viewers how to make their own dirty sodas at home.” Viral food sensations have inspired companies to capitalize on the trends, sometimes even creating new products based on what they see. In September 2020, for example, Dunkin’ partnered with TikTok star Charli D’Amelio on a limited-time drink called The Charli — cold brew with whole milk and three pumps of caramel swirl — inspired by D’Amelio’s favorite order. On launch day, Dunkin’ hit a record for daily active app users. And last year, Starbucks experimented with selling the TikTok-popular Iced Matcha Latte with Chai on social platforms. Kraft Heinz\n \n (KHC) this year launched Dip & Crunch, a burger dipping sauce packaged with “salty potato crunchers.” The idea is for people to dip a burger or sandwich into the sauce, then into the crunchers, and then take a bite — something that had apparently been trending on TikTok with some loving the trend and others questioning it. “For us to hear that debate online, then bring it to life, is an example of how we’re listening,” Sanjiv Gajiwala, then Kraft Heinz North America’s chief growth officer, told Fast Company in April. Now, you can find videos of TikTok influencers testing out the product in ads, and others reviewing it for their followers.