My Moto E5+ is stuck on bootloop, Is it Water Dmg OR bad Battery?

So I purchased this E5+ new in 2018, its been great (mostly).

A few days ago my phone got stuck on bootloop. It makes a ton of sense if the battery has just failed after all this time & use but its also possible that it was water damaged the day before as it was on a table with a sweating water bottle. When I lifted it up there was water on the back of the case but NOT inside as far as could tell. I even put a little suction on the charge port and mic openings, seemed fine. It even worked fine the rest of that day, for several hours.

How do I diagnose whether its water dmg or bad battery?

Do phones still come with that sticker inside that tells you if it got wet?

Please help.