There are two ways to get $1 fries at McDonald's: 1. Download the McDonald's app and sign up for MyMcDonald's Rewards. You will get a free large order of fries with any $1 minimum purchase. This offer is valid once per month for first-time app users. 2. Visit McDonald's on Free Fries Friday. Every Friday, you can get a free medium order of fries with any $1 minimum purchase through the McDonald's app. This offer is valid through December 31, 2023.