Catch or evolve an Eevee in Pokémon GO
Set Eevee as your buddy
Walk 10 km with Eevee as your buddy
Earn 2 Eevee candy while Eevee is your buddy
Keep Eevee as your buddy during the day
Evolve Eevee into Espeon while it is daytime in the game
Use the nickname trick once by renaming Eevee to Sakura before evolving, if you have not used it already