To get Sachet and Whipped Dream in Pokémon Sword and Shield, you will need Battle Points. These can be earned at the Battle Tower. When you have collected 20 Battle Points, you will have enough to buy Sachet and Whipped Dream.
From there, head to the Pokémon Center in Hammerlocke. Go the Pokémon Center where you spawn after using Fast Travel, then talk to the Battle Points Shop trader in the black and white sporty outfit on the right side of the Pokémon Center.
She will sell you Sachet for 10 Battle Points, and Whipped Dream for 10 Battle Points. You can use Whipped Dream to evolve Swirlix into Slurpuff by giving them the Whipped Dream and then trading the Pokémon to someone. It will then evolve into Slurpuff, and they can trade it back. Keep in mind, Swirlix is a Pokémon Sword exclusive.
Sachet will allow you to evolve Spritzee into Aromatisse. The method is similar, and you need to give the Pokémon the Satchet, then trade it with someone to evolve it. Spritzee is a Pokémon Shield exclusive.
While Spritzee is exclusive to Pokémon Shield, and Swirlix is exclusive to Pokémon Sword, they both spawn in the same places in both games. You can find these Pokémon at the following locations:
- Route 5
- Glimwood Tangle
- Giant’s Mirror
- Stony Wilderness
- Max Raid Battles
The best way to do this is to find someone who owns the game version that you don’t have and trade with each other so that you can both get the evolved forms of each Pokémon. You will both need two of the exclusive Pokémon, and either two Sachets or two Whipped Dreams to make sure you can both get the evolved forms of the Pokémon.