Where to Find and Catch Vanillite
From Pokemon Go Wiki
Vanillite are found and captured in Nest and Habitat locations.
Nests
Vanillite Nests are locations that consistently spawn Vanillite.
Habitats
Vanillite Habitats are spawn locations where Vanillite is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: