Recently Ball Guy, the Galar Pokémon League mascot from the Sword and Shield games, took over the Pokémon Twitter account to interact with trainers and give out mystery gift codes.
You'll encounter Ball Guy quite a few times throughout the story and he'll give you fancy pokéballs each time. These gifts, however, come from the mystery gift option when connecting to the internet. The codes expire in January, so there's still a few weeks to use them!
Expires January 15, 2020
K0UN1NMASC0T [Level Ball, Moon Ball, Fast Ball]
1YAHAYA [Heavy Ball, Lure Ball, Beast Ball]
0KUGAFUKA1B0RU [Love Ball, Friend Ball, Dream Ball]
Expires January 30, 2020
PRESENT [Luxury Ball x10]
How to redeem a mystery gift
1. Open your game menu in Pokémon Sword or Shield and go to "Mystery Gift."
2. Choose "Get a Mystery Gift," then select "Get with Code/Password." Your game will connect to the internet and save.
3. Type in a code listed above and receive your gift! Repeat with the additional codes.