Sun Stone evolves Gloom into Bellossom and Sunkern into Sunflora.

What is the best Pokemon to evolve with Sun Stone?

The easiest Pokemon to evolve with the Sun Stone is Sunkern, as it only requires 50 candies along with the Sun Stone to evolve it into Sunflora. So you have to focus on obtaining that particular Pokemon first. Gloom is a bit more difficult to evolve into Bellossom for a couple of reasons.

Who evolves with a Sun Stone Pokemon?

The Sun Stone is an item with very few uses, both in the mainline games and in Pokemon GO. Only five Pokemon require this stone to evolve, and four of these are currently in Pokemon GO: Gloom, Sunkern, Petilil and Cottonee. Gloom requires 100 Oddish candies and a Sun Stone to evolve into Bellossom.