Friday is National Doughnut Day — because who gets excited about National Broccoli Day? — and it turns out its history is pretty sweet.

This year marks 100 years since the Salvation Army's "Doughnut Lassies" served the treats to American soldiers on the front lines during World War I. These Salvation Army volunteers are often credited with popularizing the sweet circles, while also comforting the homesick soldiers.

In 1938, the Chicago Salvation Army revived the doughnut-making tradition as a fundraiser during the Great Depression by creating National Doughnut Day, held annually on the first Friday of June.

Many doughnut shops will be offering deals. Among them:

Salvation Army Family Stores: The Salvation Army Tampa Adult Rehabilitation Center is offering free doughnuts to early shoppers in its five Family Stores and asking them to share on social media using #GivingIsSweet. It starts at 10 a.m. Friday until the doughnuts run out at:

• 2815 S MacDill Ave., Tampa

• 13910 N Nebraska Ave., Tampa

• 27040 Wesley Chapel Blvd., Wesley Chapel

• 9926 E Adamo Drive, Brandon

• 3915 S Florida Ave., Lakeland

Dunkin' Donuts: With the purchase of any beverage, you get a free doughnut at locations nationwide, throughout the entire day on Friday.

Krispy Kreme: This chain is offering each customer a choice of any free doughnut, no purchase required, Friday. The Tampa Bay stores are also donating 25 dozen boxes of doughnuts to first responders in the area.

Little Donut House (formerly Mini Donut Mill): Get a free three-pack of mini doughnuts while supplies last Friday. 4048 W Kennedy Blvd., Tampa.

Postmates: The delivery service is giving a free dozen doughnuts to the first 5,000 Tampa dwellers who download the app and order Friday. Go to springboard.postmates.com/DONUTFAIRY. Add a dozen doughnuts to your cart from your favorite local shop and use the code DONUTFAIRY to get them for free. The company says you could be the office hero, citing a survey that found "51 percent of Americans say they think more highly of people who bring donuts into the office. Only 2 percent of people say it would worsen their opinion."

Datz Dough: The lively gastropub is giving out one classic-style doughnut per customer while supplies last Friday. Classic-style includes glazed, cinnamon, chocolate sprinkle, chocolate iced, vanilla sprinkle, red velvet, blue majestic and more. 2602 S MacDill Ave., Tampa.

The Hole Donuts: The makers of small batch gourmet doughnuts for a number of restaurants around St. Petersburg will be giving away and selling doughnuts at Saturday's St. Pete Indie Market from 11 a.m. to 3 p.m. For the summer, the market is inside the State Theatre at 687 Central Ave. N.

Jupiter Donuts: The Palm Harbor doughnut shop is giving out a free glazed doughnut with the purchase of any beverage Friday. 32130 U.S. 19 N. (727) 223-5047).

Disco Donuts: The food truck will be set up Friday at BluePearl Veterinary Partners. They will be making mini doughnuts on site from 9 a.m. to 3 p.m. and a portion of the proceeds will go to Frankie's Friends, a charity that helps people pay for expensive medical procedures for pets. 3000 Busch Lake Blvd., Tampa.

Piquant: Though known for classic French pastries, Piquant has been running a poll on social media to vote on a favorite flavor to bring back for National Doughnut Day. At press time, s'mores was winning, which means on Friday if you buy a s'mores doughnut you get a free s'mores iced coffee. Their location at 1704 N Howard Ave. does to-go orders only. (813) 251-1777.

Mini Doughnut Factory: The Tampa doughnut shop's founders, Patrick and Zezura Ruddell, are delivering doughnuts to the children and staff at the Salvation Army's Sallie House and Children's Village in St. Petersburg on Thursday, and donating a percentage of Friday's proceeds to the Salvation Army. "As the national holiday was originally created to honor women that served doughnuts to soldiers during World War I … MDF is going back to the holiday's roots," a company news release says. The shop opens at 6:30 a.m. at 2109 S Dale Mabry, Tampa.

Nicola's Donut Shop: The longtime doughnut makers are holding a contest. If your entry explaining why you love their more than 50 varieties of doughnuts gets drawn, you'll get a free dozen on Friday. 902 W Busch Blvd., Tampa. (813) 932-1303.

Contact Sharon Kennedy Wynne at swynne@tampabay.com. Follow @SharonKWn.