Want the hottest millennial talent waiting in line to work for your company? There's a simple solution that costs only $3.99 a case. Stock your fridge with LaCroix. Preferably, pamplemousse flavor. Kidding. Kind of.

Once a regional Midwestern sparkling water brand, LaCroix is making big waves across the nation. It boasts no calories, no sweeteners, no sodium or artificial anything. Though LaCroix is not the only fizzy water on the market, it's emerging as the brand of choice. Sales have more than doubled over the past two years to $225.5 million, Wall Street Journal recently reported. How did LaCroix emerge as the drink of choice for employees at Inc.-nominated company of the year Slack, and thousands of other "it" startups?

A recent piece by Digiday, a publication that covers media and marketing, points to the LaCroix social-media strategy. Specifically, a rock-solid Instagram strategy that's targeted toward millennials.

Eschew traditional advertising.

Unlike beverage giants Coke and Pepsi, LaCroix doesn't spend big on TV spots or advertising campaigns. Instead, the brand has put itself smack dab in the middle of where its target audience is. Some 28 percent of adults use Instagram, and 55% of 18-29 year olds are active on the platform, the PEW Research Center found.

LaCroix didn't just create presence on Instagram and social-media platforms. The company is extremely active and has created a sense of community there. "Through multiple social-media platforms, we strived for 100 percent consumer involvement by acknowledging all comments about LaCroix and responding to our fans on a daily basis," writes former digital LaCroix strategist Alma Pantaloukas on LinkedIn.

Align with of-the-moment hashtags.

The LaCroix hashtag game is on-point. The company encourages its followers to use branded hashtags like #LaCroixlove and #LiveLaCroix for a chance to be featured on their profile. And, they use trending hashtags to align their brand with what's hot. An example: LaCroix is reposting user photos with the hashtag #Whole30approved. Whole30 is a month-long "eating healthy" program that eschews processed foods, sugar, dairy, and grains. As you can imagine, a lot of foods aren't permitted on the program. But LaCroix is.

These tactics not only attract new users to their social-media circle, but also show LaCroix as a social-media savvy brand that "gets" its target audience.

Target micro-influencers.

If you're not sick of hearing about social-media influencers yet, then you somehow must have been avoiding the internet for the past year. While some brands pay thousands of dollars for Instagram users with large followings to feature their products, LaCroix has adopted a reverse approach to finding and rewarding influencers.

LaCroix first looks for users who have already tagged their brand. They aim to engage with all of them. And if you're lucky, you might get a voucher for a free case of LaCroix in the mail. You don't need to have a million followers to be so lucky. "They're actively sharing content on their feed from Instagram users with as low as 150 followers," social media director at PM Digital Toni Box told Digiday. "It gives them a more authentic and community-based feel."