Pairs of Brazilian popular Havaianas brand sandals are displayed in Sao Paulo, March 18, 2003. Here's how to score a free smoothie for National Flip-Flop Day. Reuters

It's finally warm enough to wear flip-flops, so why not take advantage of your summer footwear? You can score free items if you celebrate National Flip-Flop Day on Friday. Here's how:

Walk into any Tropical Smoothie Cafe while wearing flip-flops and get a free Jetty Punch (strawberry-banana) smoothie, no questions asked. Stores will give them out from 2 p.m. to 7 p.m. or as long as supplies last. While you're there, consider donating to Camp Sunshine, the cafe chain's national charity partner.

At Cumberland Farms you can choose any size frozen or fountain drink and get it for free at checkout during Free Chill Zone Day. Cumberland Farms has about 600 locations along the East Coast, and since last year it's sold enough drinks to fill seven Olympic swimming pools, according to a news release.

At Six Flags, bring a new pair of flip-flops to donate and get free admission to Hurricane Harbor. You'll also get a bracelet that lets you ride the Hammerhead, Barracuda, Typhoon and Vortex at a special time. Details here.

If you're in Philadelphia, wear flip-flops to the drive-thru of any Swiss Farms grocery store and get a free 16 oz. ThirsTea Now drink. Check out their locations here.

Near Atlanta? Check out Oka-B's second annual warehouse sale on Friday from 10 a.m. to 4 p.m. Flip-flops start at $5, and adorned sandals are $7. If you can't get there in person, order online, where shipping is free on orders that exceed $75.

It's not technically on National Flip-Flop Day, but it's a deal all the same: Old Navy is holding its annual flip-flop sale on Saturday. You can get a free pair if you're one of the first 50 customers at a store, which open at 7 a.m. If you're a little later, flip-flops are $1.