McDonald's reveals locations giving away 10K bottles of 'special sauce'

Jan. 25 (UPI) -- Ever wonder what McDonald's puts in its Big Mac "special sauce?" Well, the burger giant won't give away that secret -- but it will give away thousands of bottles of the famous concoction on Thursday.

The restaurant announced the giveaway this week after unveiling two new versions of the iconic Big Mac sandwich -- a smaller Big Mac Jr. and larger Grand Big Mac.

Wednesday, the chain announced which U.S. locations are involved in giving away 11.4-ounce bottles of the legendary condiment.

"The Big Mac Sauce is unique to McDonald's and includes a classic combination of ingredients," McDonald's spokeswoman Becca Hary said in a statement. "The Bic Mac Sauce remains timeless and customers around the world continue to enjoy its signature taste."

You can find the nearest location by using the "Special Sauce Finder" app on your smartphone -- or by consulting this list.

Want sauce? 2️⃣ways! iMessage app (https://t.co/pTbUJFmaDW)+in-restaurant phrase OR our livestream on 1/26 @ 1pm CT! https://t.co/vjGftuJ5pr pic.twitter.com/UjwAAH6GFD

— McDonald's (@McDonalds) January 25, 2017

When you arrive at a participating McDonald's store, give the special code -- "There's a Big Mac for that" -- for the chance to take home a bottle.

Locations in 44 states and Washington, D.C. are involved in the giveaway. No restaurants in Rhode Island, Nebraska, Oregon, Montana, Wyoming or New Hampshire are featured in the promotion. Quantities vary by location, the restaurant chain said.

Big Mac sauce has been a top secret McDonald's staple since the sandwich was introduced in 1968. The ingredient was further made famous by television commercials, starting in 1975, that boasted "two all-beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun."

While many say it tastes very similar to thousand island dressing, McDonald's has for years insisted that the sauce has more to it.

Thursday will mark the first time McDonald's has ever given out quantities of the signature sauce. It has never been sold to customers, either.