Dunkin customers have just two days left to take advantage of limited menu offer see the spec

DUNKIN' fans only have a couple of days left to take advantage of a special offer – but not every menu item will qualify for the deal.

Throughout the entire month of May, the fast-food chain has been offering what it calls "free coffee Mondays."

Customers who make any purchase qualify for a free medium coffee.

But since the month is waning down, only two Mondays are left to take advantage of the deal.

So you'll need to either act today or Monday, May 29.

HOW TO TAKE ADVANTAGE OF THE REWARD

But keep in mind, not everyone can take advantage of the deal on Mondays.

It might be best to go with something cheap like a three-count pack of munchkins, which costs $1.59.

Most coffees, including the fan favorite Butter Pecan Swirl, will qualify for the free offer through the Dunkin' app.

Dunkin's midnight coffee will also satisfy the offer.

However, some others may not.

For example, when The U.S. Sun tried to check whether the frozen coffee would work, the cost for a medium stayed the same at $5.39.

Keep in mind that prices and availability can vary by location.

But generally speaking, Dunkin' fans will want to join the app if they haven't already.

That's because there's exclusive access to a variety of other offers that aren't available to the general public.

Plus, you can place an order through your phone and have it ready for pickup by the time you arrive at the store.

To see what other deals Dunkin' has through the app, make sure to head to the offers section.

Another deal under the category is save $3 on a sausage-egg-and-cheese breakfast sandwich when ordering a medium or large coffee.

In other news on coffee chains, Starbucks has discontinued a popular drink.