To name an Eevee in Pokemon Go, you can use a specific nickname to guarantee its evolution into a specific Eeveelution. However, this naming trick only works once per evolution. Here are the nicknames you can use for each Eeveelution:
- Vaporeon: Rainer
- Flareon: Pyro
- Jolteon: Sparky
- Espeon: Sakura
- Umbreon: Tamao
- Leafeon: Linnea
- Glaceon: Rea
- Sylveon: Kira
To use the naming trick, simply rename your Eevee with the corresponding nickname and then evolve it using 25 Eevee candy. Make sure to double-check the silhouette of the Eeveelution before pressing the "Evolve" button.