On June 17, you'll get a complimentary smoothie when you wear flip-flops to any Tropical Smoothie. Credit: Tropical Smoothie Café via Facebook

So National Flip Flop Day is a thing, at least for Tropical Smoothie Café. Locals who wear theirs to any Tropical Smoothie location between 2 and 7 p.m. Friday will snag a free Jetty Punch smoothie.

While claiming their 24-ounce freebie, guests are also encouraged to make a donation to Camp Sunshine, a free Maine-based retreat for children with life-threatening illnesses and their families

Donations from $1 to $4 will earn a paper flip-flop sign that will hang inside the fast-casual restaurant, but for those who'd like to make a bigger donation, reusable mugs will be on sale for $10. A flip-flop-shaped key fob (available for a donation between $5 and $9) will even get you a 30 percent discount on Feelgoodz flip-flops.

This year, Tropical Smoothie aims to donate $1 million through its annual holiday and other fundraising efforts. The Bay area operates cafés in Largo, St. Petersburg, Tampa and Brandon, among other locales.

This article appears in Jun 9-16, 2016.