Used when any choice among a set is acceptable or will do. Often implies indifference or that all options are equally fine.
See also: どれ
どれでも好きなのを選んでいいよ。
You can choose whichever one you like.
この中からどれでも一つ持って行ってください。
Please take any one from these.
Any of the drinks is fine with me.
この中からどれでも好きな本を選んでください。
Please choose whichever book you like from these.
I don't mind which seat I get.
どれ is the plain interrogative 'which one?', while どれでも adds でも to mean 'any one, whichever' with no question intended.
Compound of どれ (interrogative 'which') + でも (particle meaning 'even' or 'any'). The combination yields the meaning 'any one' or 'whichever'.