Because there are no specifics in your question, I have no idea what your projects might be. So I will pretend this question is about future side projects and not current side projects.
Conveniently, this allows me to suggest the simplest thing that might work:
Do the simplest thing that might work.
The easiest way to handle authentication is to choose a project that doesn't require.
Text files are the simplest databases.
Github pages is a simple way to host a site.
HTML, CSS, and Javscript don't require a backend, just a web server.
A sideproject doesn't need to look like the thing that you work on all day at a workplace. When there's money on the line, relational databases and robust authentication can have economic rationales. IF there's no money involved, and maybe no users, why bother? Unless you want the practice doing what you already know and want to avoid doing harder things like getting users (and maybe making money).
Good luck.
