For water sources and offline maps Osmand and MapsMe allow to search for water sources (taps, wells or public bathrooms f.e.). For the public restrooms you'll even see open times if someone added them.
I made a demo for you, I'll PM you the admin link, however here's the editable version, as admin you can tinker around with the marker settings as well. Feel free to test it out. If you want it offline on your phone you can click on tools and then export it to GPX and load into Osmand or MapsMe, if you export once with the phone chagers and once with the wall chargers visible you'll even be able to set them up differently. It still lacks conveinient updating systems, but it's definitely possible to make an Osmand Add-On. Oh almost forgot, if people want to use it around the US or even around the world it would make sense to make your own map to keep the maps working well on lower-end machines and smartphones.
Edit: the same works the other way around: you can map the chargers on your phone and upload the file to facilmap. I know this isn't really a convenient app, but it works.
Back to Osmand and MapsMe, they are basically both just using OpenStreetMap as a basis for all of the map data. You could go to the forum or a mapper meeting and propose a tag for public outlets, I think it would be a cool thing to have.
Facilmap does that. It's free and based on OSM data.
Go to 'Collaborative Maps' in the upper right corner and select 'Create a New Map.' Record the Admin / Editable / Read-only links, fill in the other data, and click 'Create.'
Add a marker, click it, and edit the data to add labels. You can also add routes.
Share the link with your collaborators.
Here's the repo, for any interested developers. I don't know the creators and have no affiliation with this project, I'm just an interested user.
I made an effort to map incidents that can be seen at https://facilmap.org/riotmap. It's only somewhat comprehensive for Minneapolis, essentially useless for this question other than in Minneapolis. I recorded 238 incidents of looting or property damage in Minneapolis, of which 60 involved arson.