First step? Keep your receipt
Once upon a time, when I was a college student living in Somerville, Massachusetts, my house was within 1.5 miles of five different Dunkin' Donuts. The closest Dunkin' was right down the block, a mere 0.2 miles away according to Google Maps, so it should come as little shock that over the course of my four years, I became something of an expert in Dunkin' Donuts hacks. I visited a Dunkin' Donuts every single day before class, and my order was always the same: a medium coffee and a free Dunkin' Donuts doughnut. Yes, I figured out how to get a free Dunkin' Donuts doughnut every day, and you can do it, too. You don't even have to be a broke college student!
The first step? Go to Dunkin' Donuts and order something. Anything, really. It could be a single doughnut or an extra-large iced coffee or a breakfast sandwich. What's important here is that you ask for and keep your receipt.
That's because at the bottom of every Dunkin' Donuts receipt, there's a URL to a survey you can fill out online. The site itself is really straightforward, and the survey asks you about your experience, your order, whether or not you like Dunkin' Donuts. It takes about five minutes, and no matter how you answer, at the end of the survey, you'll get a five-digit validation code. Write that code at the bottom of your receipt, and put it in your wallet.
When you go to Dunkin' Donuts the next day and order a medium coffee or larger, hand over the receipt with the code to the clerk, and you get a doughnut for free. That's literally it. You can walk out of that store with a free breakfast and turn it up like you're Gronk—or David "Big Papi" Ortiz, depending on which Boston sports team you prefer.
Now, there is some red tape associated with this Dunkin' Donuts hack. The first being that you have to fill out the survey within 72 hours of your purchase—so don't forget about it. You also have to go back to the same Dunkin' Donuts store in order to redeem your free doughnut. The code won't be valid at another location. But that's part of the reason this hack worked so well for me in college; I was going to the same Dunkin' Donuts before class every day anyway. (As a result, I got to know some of the customers by sight. Like that one woman who always ordered an "extra-large regular iced with extra, extra sugar," like she was straight out of that Saturday Night Live sketch.)
Your free doughnut also isn't totally free. Like, you can't just roll up with your receipt to your friendly, neighborhood Dunkin', and ask for a free doughnut. You've got to order a medium or larger beverage to go along with the free doughnut. But, again, when you're already ordering a medium coffee every single day like I was, it's not an additional burden. Besides, who wants to eat a doughnut without coffee anyway?
The real "hack" here, though, is that there's no limit to the number of free doughnuts you can get. When you order a coffee and give the code and get a free doughnut, you'll get another receipt with another survey. Fill it out again, go back the next day, and order another doughnut with your coffee. It feels like you're gaming the system, which are you kind of doing, but it'll work every time. And it's not like Dunkin' Donuts doesn't know about this hack to get free doughnuts; the rules are listed right on their website.
Just be sure to give your local Dunkin' Donuts a five-star rating every time. After all, these are the folks who are giving you a free doughnut every single day. It's the least you can do.