During the Pokémon Japan Championships 2021 Game Division broadcast on July 18th, 2021, a serial code was revealed that allowed all players of Pokémon Sword and Shield to receive a Cotoise. This Cotoise's ID is Clara (クララ) and is named after the one Kōhei Sakurai used to help them win the Pokémon Japan Championships 2020 Video Games Masters Division. It will be available to claim from July 18th, 2021 until July 19th, 2021. The code is: PJCS2020CHAMP

Cotoise Event Pokémon Details:

OT: 210718
ID: クララ
Ability: Drought
Hold Item: Sitrus Berry
Moves: Burning Jealousy, Body Press, Yawn, Protect

Source: https://www.youtube.com/watch?v=MIHrV0AJMaA