Pokémon GO Evolution Items
Evolution items are required to evolve certain Pokémon.
Currently there are 8 evolution items:
Sun Stone
In game description:
A peculiar stone that can make certain species of Pokémon evolve. It burns as red as the evening sun.
Pokémon that use a 
Sun Stone to evolve:
Oddish -> 25
-> 
Gloom -> 100 +Sun Stone-> 
Bellossom
Sunkern -> 50 +Sun Stone-> 
Sunflora
Cottonee -> 50 +Sun Stone-> 
Whimsicott
Petilil -> 50 +Sun Stone-> 
Lilligant
Helioptile -> 50 +Sun Stone-> 
Heliolisk
How to get Sun Stones:
After reaching level 10 a player can rarely get Sun Stones from spinning Poké Stops or Gyms, opening 
gifts or by completing a 7 day spin streak which guarantees at least one evolution item from the Johto region (Sun Stone, 
King's Rock, 
Metal Coat, 
Dragon Scale, 
Upgrade).
King's Rock
In game description:
A rock that can make certain species of Pokémon evolve. It looks like a crown.
Pokémon that use a King's Rock to evolve:
Poliwag -> 25 -> 
Poliwhirl -> 100 +King's Rock-> 
Politoed
Slowpoke -> 50 +King's Rock-> 
Slowking
How to get King's Rocks:
After reaching level 10 a player can rarely get King's Rocks from spinning Poké Stops or Gyms, opening gifts or by completing a 7 day spin streak which guarantees at least one evolution item from the Johto region (Sun Stone, King's Rock, Metal Coat, Dragon Scale, Upgrade).
Metal Coat
In game description:
A coating that can make certain species of Pokémon evolve. It is a special metallic film.
Pokémon that use a Metal Coat to evolve:
Onix -> 50 +Metal Coat-> 
Steelix
Scyther -> 50 +Metal Coat-> 
Scizor
How to get Metal Coats:
After reaching level 10 a player can rarely get Metal Coats from spinning Poké Stops or Gyms, opening gifts or by completing a 7 day spin streak which guarantees at least one evolution item from the Johto region (Sun Stone, King's Rock, Metal Coat, Dragon Scale, Upgrade).
Dragon Scale
In game description:
A scale that can make certain species of Pokémon evolve. It is very tough and inflexible.
Pokémon that use a Dragon Scale to evolve:
Horsea -> 25 -> 
Seadra -> 100 +Dragon Scale-> 
Kingdra
How to get Dragon Scales:
After reaching level 10 a player can rarely get Dragon Scales from spinning Poké Stops or Gyms, opening gifts or by completing a 7 day spin streak which guarantees at least one evolution item from the Johto region (Sun Stone, King's Rock, Metal Coat, Dragon Scale, Upgrade).
Upgrade
In game description:
A transparent device that can make certain species of Pokémon evolve. It was produced by Silph Co.
Pokémon that use a Upgrade to evolve:
Porygon -> 25 +Upgrade-> 
Porygon2
How to get Upgrades:
After reaching level 10 a player can rarely get Upgrades from spinning Poké Stops or Gyms, opening gifts or by completing a 7 day spin streak which guarantees at least one evolution item from the Johto region (Sun Stone, King's Rock, Metal Coat, Dragon Scale, Upgrade).
Sinnoh Stone
In game description:
A special stone originally found in the Sinnoh region that can make certain species of Pokémon evolve. It is very tough and has a beautiful sheen.
Pokémon that use a 
Sinnoh Stone to evolve:
Lickitung -> 100 +Sinnoh Stone-> 
Lickilicky
Rhyhorn -> 25 -> 
Rhydon -> 100 +Sinnoh Stone-> 
Rhyperior
Tangela -> 100 +Sinnoh Stone-> 
Tangrowth
Elekid -> 25 -> 
Electabuzz ->100 +Sinnoh Stone-> 
Electivire
Magby -> 25 -> 
Magmar -> 100 +Sinnoh Stone-> 
Magmortar
Porygon2 -> 100 +Sinnoh Stone-> 
Porygon-Z
Togepi -> 25 -> 
Togetic -> 100 +Sinnoh Stone-> 
Togekiss
Aipom -> 100 +Sinnoh Stone-> 
Ambipom
Yanma -> 100 +Sinnoh Stone-> 
Yanmega
Murkrow -> 100 +Sinnoh Stone-> 
Honchkrow
Misdreavus -> 100 +Sinnoh Stone-> 
Mismagius
Gligar -> 100 +Sinnoh Stone-> 
Gliscor
Sneasel -> 100 +Sinnoh Stone-> 
Weavile
Swinub -> 25 -> 
Piloswine -> 100 +Sinnoh Stone-> 
Mamoswine
Ralts -> 25 -> 
Kirlia -> 100 +Sinnoh Stone+ Male -> 
Gallade
Budew -> 25 -> 
Roselia -> 100 +Sinnoh Stone-> 
Roserade
Duskull -> 25 -> 
Dusclops -> 100 +Sinnoh Stone-> 
Dusknoir
Snorunt -> 100 +Sinnoh Stone+ Female -> 
Froslass
How to get Sinnoh Stones:
Sinnoh Stones have a chance to be obtained from 
Research Breakthroughs, fighting against a Team Leader (1 time daily) or other players (3 times daily) or from winning in the GO Battle League.
Unova Stone
In game description:
A rare stone that originates from the Unova region that can make certain species of Pokémon evolve. It is known for its intertwined black-and-white appearance.
Pokémon that use a 
Unova Stone to evolve:
Pansage -> 50 +Unvoa Stone-> 
Simisage
Pansear -> 50 +Unvoa Stone-> 
Simisear
Panpour -> 50 +Unova Stone-> 
Simipour
Munna -> 50 +Unova Stone-> 
Musharna
Minccino -> 50 +Unova Stone-> 
Cinccino
Tynamo -> 25 -> 
Eelektrik -> 100 +Unova Stone-> 
Eelektross
Litwick -> 25 -> 
Lampent -> 100 +Unova Stone-> 
Chandelure
How to get Unova Stones:
Unova Stones have a chance to be obtained from Research Breakthroughs or from winning against a Team GO Rocket Leader or Giovanni.
Gimmighoul Coins
In game description:
A coin with a mysterious air. It seems to have originated in the Paldea region.
Pokémon that use 
Gimmighoul Coins to evolve:
Gimmighoul -> 999Gimmighoul Coins-> 
Gholdengo
How to get Gimmighoul Coins:
Gimmighoul Coins can be obtained by catching Gimmighoul, walking with Gimmighoul or Gholdengo as your Buddy, spinning a Poké Stop with an active 
Golden Lure Module or by obtaining a Golden Lure Module while already having one in your Inventory.