Tropical Smoothie Cafe has hosted a National Flip Flop Day even year since 2007, and this year’s installment is happening on Friday, June 15, 2018.

Visit one of their more than 600 locations in 44 states and you will get a free Sunshine Smoothie anytime between 2pm and 7pm. The Sunshine Smoothie consists of a combination of mangos, bananas, oranges, and pineapple.

All you have to do to earn that free smoothie is wear sandals. That’s it. Show your toes, and you’re all set. It’s all part of the Cafe’s effort to raise $1 million for Camp Sunshine, a cost-free, year-round camp for kids with life-threatening illnesses and their families. The smoothies are 100% free, but customers are encouraged to contribute a little to Camp Sunshine to help the smoothie shop meet its goal.

“These families have had to endure some of life’s most challenging circumstances, and we’ve seen how much Camp Sunshine means to them,” Mike Rotondo, CEO of Tropical Smoothie Cafe, said in a statement. “Some days, you have to create your own sunshine, and that’s the beauty of Camp Sunshine, it creates sunshine for these families.”

The summer is off to a good start.