I've used Eevee on my only team, on the username Soul Dew Latias, and I've gotten pretty high up with it. Here's a replay with a basic idea of Eevee's purpose.Maybe you could use max investment in HP & Spd along with Adaptability + Extreme Evoboost + Explosion (or Eruption if you want to troll) but other than that, it's no use since Baton Pass is not allowed. Besides, since everybody uses E-Spd with E mons, it can get predicted rather easily. Do you have any replay of this being used competitively?
https://replay.pokemonshowdown.com/gen7alphabetcup-687066046