An extremely valuable Gold Bottle Cap item can be claimed for free right now in Pokemon Sword & Shield, but you'll need to act fast, as it's only available until December 14.
IVs and EVs are hidden stats in the Pokemon series that determine how powerful a Pokemon will be. If you don't care about competitive battles against other players, then you can easily ignore IVs and EVs, as they don't come into play in the single-player mode and don't influence collecting Pokemon. IVs are Individual Values, which determine how a stat will grow, and EVs are Effort Values, which are bonuses earned from winning battles against other Pokemon.
The later Pokemon games made it easier to influence the IV stats of a Pokemon, with the help of Bottle Cap items. You can claim a free Gold Bottle Cap in Pokemon Sword & Shield will the help of a code that will remain active until December 14. According to Serebii, it can be claimed as a Mystery Gift.
In order to claim the Gold Bottle Cap, you need to be connected to the Internet. Go into the Mystery Gift menu, select "Get a Mystery Gift", select "Get with Code/Password", then type PC2F1NALSSTREAM into the prompt. You can then claim the Gold Bottle Cap, which will appear in your inventory.
Bottle Caps are valuable items in the Pokemon series. To use them in Pokemon Sword & Shield, you need to finish the game and access the Battle Tower. Once a Pokemon has reached level 100, you can trade a Bottle Cap to fully train one of its IV stats, as if it was a perfectly bred Pokemon. The reason Gold Bottle Caps are so valuable is that they can be used to max out the stats of a single Pokemon. You should claim the Gold Bottle Cap while it's available, even if you don't care about competitive battles, as they can be given to Pokemon as held-items and traded over, making them valuable to other players.
The free Gold Bottle Cap can be claimed in Pokemon Sword & Shield until December 14, 2020.
Source: Serebii