Hey, I don't know if this has been posted, but I might as well put this tip out there if it will help someone.

I had like $100 in iTunes gift cards that I never used since I went android and have spotify. However, you can still use this money for your Pokémon Go excursions!

You need a trusted friend (my sister in my case) with Pokémon Go on their iPhone. First add the iTunes GC to their apple account. Then have them log off on Pokémon Go and then log in. Your account will be able to access their apple account credit. Then purchase whatever you want (lucky eggs and incubator for dayzzzz). Then log back off.

However, your Pokémon Go account login will be saved in their app so be wary of that. This may seem intuitive for some, but if it helps someone out then why the duck not? Go catch em all!