Considering how repairable earbuds usually are, it would be possible to fix them, but incredibly difficult mainly due to the size of the parts. Also do consider that almost everything within the earbuds is most likely damaged from the water, meaning that you would have to replace basically every part within them, especially considering how the earbuds aren't rated to handle being washed, let alone the case.
I'd believe you'd be better off just getting a replacement.