anything is fine; it doesn't matter what
Colloquial expression used when the speaker is indifferent to the choice or outcome. Often implies a relaxed or slightly dismissive attitude. Compare with 何でもいい, which is more neutral.
See also: 何でもいい
Anything is fine for lunch.
It doesn't matter what the result is. The important thing is to try.
Variant using 良い for いい; slightly more formal or emphatic in writing.
Colloquial contraction of 何だって (what, whatever) + いい (good, fine). The って is a casual quotative/emphatic particle derived from と.