Saturday is National Drive-Thru Day, and Wendy’s is celebrating. 

The fast food chain is offering customers a free Frosty or a free order of fries in any size with a purchase. 

The offer is not available on delivery orders and can only be found on the Wendy’s mobile app.

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According to the offer in the app, Wendy’s is only giving away the free treats on Saturday. The chain is also limiting the offer to one per customer. 

On Saturday, Wendy's is offering customers a free Frosty or a free order of fries in any size with a purchase, for National Drive-Thru Day. (iStock)

On Saturday, Wendy's is offering customers a free Frosty or a free order of fries in any size with a purchase, for National Drive-Thru Day. (iStock)

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According to Thrillist, it’s no surprise that Wendy’s is celebrating National Drive-Thru Day. 

The chain claims to have introduced the first modern drive-thru in 1970, which Wendy’s founder Dave Thomas called the "Pick-Up Window," according to the company website. 

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Aside from celebrating National Drive-Thru Day, Wendy’s recently added a spicy new sauce to its menu. 

The chain added Ghost Pepper Ranch dipping sauce across the country, FOX Business reported earlier this week. 

The sauce is intended to be paired with Wendy’s spicy chicken nuggets, according to the company’s announcement.