Evolution items in Pokémon Go can be difficult to come by in the mobile game. You’re not going to find them too often when exploring the game. You’ll need to use these items to evolve certain Pokémon, and the Sun Stone is one you’ll need.
If you’re on the hunt for a Sun Stone, your best bet is to try farming it from any nearby Pokéstops. Your next best alternative will be to complete special research or timed research tasks from weekly events. These are the most common ways to acquire the Sun Stone item.
Not every weekly timed or special research contains these evolution items. Typically, they’re given as a reward when that item has something to do with a particular Pokémon is featured. This normally happens if a Pokémon has their shiny version release, or they’re going to be one of the increased spawns players can capture throughout the week.
When you’re still having trouble acquiring a Sun Stone, you have the chance to receive one by completing the weekly field research tasks. You can do this by finishing a field research task every day for seven days in a row. By the end of the streak, you’ll have a chance to capture the monthly breakthrough research Pokémon and several items. One of them can be an evolution item. It’s not guaranteed to be a Sun Stone or any of the others, but there’s a small chance of it happening.
While it’s not the best chance to receive one, these are the many ways to receive a Sun Stone and the other evolution items in Pokémon Go.