Many Pokemon GO players are reporting of getting Pokemon Gen 2 Evolution items using this simple method. It seems spinning the same Pokestops every day has its rewards.
Seventh Day Spin Streak
A lot of Pokemon Go players are claiming that a Gen 2 evolution item is included after spinning a Pokestop at least once a day for a week. Some have posted their findings in social media groups such as Reddit. YouTube Pokemon GO presenter Trainer Tips also confirmed that he got a dragon scale from his seventh day spin streak.
Not For Everybody Though
A number of unlucky Pokemon GO players though reported that they have not received any Gen 2 evolution item. There is no hard data yet to calculate the possibility of getting one. On the other hand if it's an RNG thing, it's quite generous. Based on the players' reports, it seems about half who tried it got a Gen 2 evolution item. Still, an evolution item usually turns up after several attempts. There is also the possibility that Niantic has not yet finished setting up the frequency drops of the items.
About The Gen 2 Evolution Item
Gen 2 evolution items are needed for evolving some of the Gen 2 Pokemon. There are five such items namely Dragon Scale, Kings Rock, Metal Coat, Sun Stone and Upgrade. The Dragon Scale can evolve a Pokemon like the Seadra into a Kingdra. Meanwhile, the Kings Rock can transform water type Pokemon Poliwhirl to a Politoad and the Slowbro into a Slowking.
The Metal Coat can evolve steel type Pokemon such Onix to Steelix and Scyther to Scizor. A guide about the Metal Coat and related Pokemon is also available. On the other hand, the Sun Stone evolves mostly grass type Pokemon. This includes the Gloom evolving to a Bellossom and Sunkern to Sunflora. Finally, the Upgrade usually evolves the Porygon to a Porygon 2.