How to reset Password without eMail?

Hi, a few months ago, I created 5 niche sites in WordPress and forgot to write the log-ins down.
Now, months later, I don’t know how to retrieve it, as I have no clue what email they are linked to. (they are 10 article niche sites, so no audience communication)
Since I own and have acces to both the site where the domains, and where the actual site is hosted on, I have considered re-installing WordPress, in hopes that I can change a new login, however it would be a shame, since I have put at least 20-30 hours into designing/creating them..