Assuming it is on a BMW rim it would fit.
I bought an unused 17" one with jack and wheelbrace for my previous E86 for quite a bit, but never got around to fitting non run-flat tyres. :roll:
But I don't think it would fit my MC so I've got a full-size wheel as a spare now, just very little boot space! But even if you fitted a space-saver you'd need to get a full size wheel in the boot anyway, or abandon it.