From now until the end of year you can get an order of Medium French Fries at Mc Donalds. Here's how "Free Fries Friday" works all you have to do is buy at least $1 worth of food on the app on a Friday, and you'll get a free medium-sized fries with your order. The deal is good every Friday for the rest of the year, but you can only get one Free Medium Fries each Friday.