If you have ever seen an episode of the cult TV show Mad Men, you'll be familiar with this scenario: Don Draper, after a long day (well, sometimes just the morning commute), walking into his office, opening up his bar, and pouring a stiff drink to unwind. In meetings, next to the coffee and pastries would be an array of liquors on offer for anyone who wished to partake. And every lunch and dinner meeting would be punctuated by cocktails and wine.

For some, this scene is something that is a cultural relic -- it went out of fashion with bellbottoms and cigarette ads on television. However, in startup culture, whether it is nostalgia or something else, at least part of it is making a comeback.

89 percent of Millennial employees cite workplace happiness as a reason they stay with a job, with 66 percent saying that unique perks like food and beer are what keep them interested.

At my former company, Evernote, we had something we called "Beer Friday." In all of our offices around the world, we instituted an in-office happy hour where we had craft brews available (many brewed by employees of the company,) and elaborate Charcuterie plates. These gatherings were used as a way to wind down at the end of a busy week, and for people in different departments to mingle with each other.

We kept the keg and tap on site all the time -- and at least during my time -- there wasn't anyone who abused the privilege. Other companies, like Yelp and Sendgrid, have keg fridges available all the time, while The Muse goes further and offers Whiskey during their Friday sessions. This has led to some companies like the Arnold Worldwide Ad Agency to install beer vending machines.

Enter Anheuser Busch. With their new Office Bud-E program, Andrew Green, Head of Innovation hopes to help companies on two fronts. He explains, "A lot of startups and communities are starting to have happy hours in the office, and we thought as Anheuser Busch we can certainly find a way to play in that space and add value."

Eligible companies get a free wi-fi enabled refrigerator, designed to hold -- you guessed it -- beer. Office managers purchase beer from local distributors -- not from Anheuser Busch directly, at their own pace. There is no subscription required, and there's no charge for the service.

For this, the data is valuable to Anheuser Busch. They will be able to quantify how much beer is purchased specifically for office usage -- something no one has been able (or possibly tried) to measure before. "This also functions as a regular fridge," added Green. "If someone puts their lunch in there, that's useful data as well." He explained that the sensors would be able to measure that something foreign is in the machine, and the rough size and shape.

Currently, they are only in certain test markets on the east coast. However, he mentioned, "We're now preparing for a national launch in states where our delivery partners operate." All interested companies are encouraged to apply at the Bud-E website. 

For those considering an office happy hour policy, here are a few things to keep in mind:

1. Heed your State and Local Laws

While it is generally assumed that adults will act responsibly, especially in an employee setting, 18 states place liability on the host who serves the alcohol - which means your company.

At Yelp, their Kegerator requires people to sign in before using it -- giving them detailed records of how much it has been used (and by whom.) Consider the type of policy that is right for you.

2. Make It Optional

Even if your happy hour is taking place during work hours, if there is alcohol being served, there may be employees who cannot attend at all. Allow them a discreet way out.

For those who abstain from drink, ensure there are non-alcoholic refreshments available as well.

3. Encourage Non-Work Conversations

While it may be tempting to chat about the report that is overdue, or the client deadline coming up, a happy hour is a time for relaxing and socializing.

Not great with topic ideas? At Evernote, we created "Evernote University" -- a series of extracurricular clubs offered to employees, which helped stir conversation.

4. Let it Go

At some point, your company may outgrow "Beer O'Clock." This doesn't preclude teams from going out together, though, so continue to encourage social groups as your company grows.

In all, happy hours are a great way for your employees to break away from their desks and bond with each other. And that, really, is the key to successful employee engagement.