whats the best way for a teenager to make money?

It really depends on what you enjoy doing. Coding is the easiest, most easily accessible and probably reliant way of making money, as a teenager or adult even, if you know what you're doing a little bit. It's also probably the skillset with the most free learning options out there, you can find a tutorial for just about anything regarding any programming language.
I personally would suggest looking into web development, you will ALWAYS find someone looking for some guy to make a website for him. Always. And most of them would gladly let a teenager do it, if it meant paying a bit less (some web developers really cost a lot).

When I was 16-17 I used to browse random small companies in my area's websites (not IT focused, obviously), find some with ugly ass websites from the early 2000s or 2010s and message them offering a redesign of their website with some buzzwords they wouldn't really understand (like responsive design, better SEO strategy etc..) and showing some graphs I found on google about how "better website = more traffic = more money" and stuff like that (which is true btw, you're not even bullshitting).
Or sometimes, I would simply offer to fix some mistakes or make the design just a bit better.

I would make anything from 100-300$ for some quick edits that would take me a couple of days of work, or even up to 1200$ once for a full website "from scratch" (obviously it was mostly bootstrap). I did this for a year basically and on average I'd get 400-700$ a month, depending on if I found clients or not. Oh and obviously I also posted on forums, facebook groups etc... Now this was some 7-8 years ago, things might have changed but I don't see why one could not do this anymore. If anything, maybe the required skills to make something even close to "up-to-standard" quality is a bit harder to learn, but nothing that a couple of months of youtube tutorials can't provide.