To get Sachet and Whipped Dream Pokémon Sword and Shield, you will need Battle Points. These can be earned in the Battle Tower. After collecting 20 battle points, you will have enough to buy the packet and the assembled dream.
From there, go to the Hammerlocke Pokémon Center. Go to the Pokémon Center where you spawned after using Fast Travel, then talk to the Battle Points Shop trader in the black and white sports outfit on the right side of the Pokémon Center.
He will sell you Packet for 10 Battle Points and Whipped Dream for 10 Battle Points. You can use Whipped Dream to turn Swirlix into Slurpuff by giving them the Whipped Dream and trading Pokémon with someone. It will then evolve into Slurpuff and they can trade it. Please note that Swirlix is an exclusive Pokémon Sword.
Sachet will allow you to transform Spritzee into Aromatisse. The method is similar and you have to give the Pokémon the Satchet, then trade it with someone to evolve it. Spritzee is an exclusive Pokémon Shield.
While Spritzee is exclusive to Pokémon Shield and Swirlix is exclusive to Pokémon Sword, both spawn in the same places in both games. You can find these Pokémon in the following locations:
- Path 5
- Tangle of Glimwood
- Giant's Mirror
- Stony desert
- Max Raid Battles
The best way to do this is to find someone who owns the version of the game you don't have and trade with each other so that you can get both evolved forms of each Pokémon. You will both need two of the exclusive Pokémon and two packets or two mounted dreams to make sure you can get both evolved forms of the Pokémon.