Sprint is currently giving away a number of items to Pokémon GO players who visit Sprint stores. While supplies last, customers with an Android smartphone can redeem a code to receive Great Balls, Lucky Eggs and Incense. This offer is supposed to run until December 31, 2017 at 11:59 pm ET – so you have plenty of time if you want to take advantage of it. Sprint is the exclusive U.S. wireless partner for Pokémon GO.
Source: My Trainer Rewards