SAN ANTONIO - Calling all fans of Whataburger, sweet treats, and, of course, those who enjoy free things.

For a limited, one-day offer, Whataburger is celebrating its 74th birthday by offering a free 20-ounce birthday cake-flavored milkshake on Thursday to customers who download their app and create a rewards account.

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If you take advantage of the restaurant's birthday freebie, Whataburger SVP and Chief Marketing Officer Scott Hudler said the milkshake will look like a "party in a cup" and "taste like fun."

However, if you can't make it out Thursday for the freebie, KSAT has great news for you.

Whataburger plans to release the birthday cake flavor after their birthday celebration on a limited-time basis.