I have more side projects than I'll ever be able to finish. When I do finish them (or at least get a mvp), I have no idea how to market them, and in many ways, I don't even want to. I'm worried that it will kill the fun of it for me.

It is smart that you bring up marketing. You can solve that problem.
Build marketing into your roadmap.
Develop an app that solves a problem or makes people's lives easier. You will still need marketing but there must be a need. If you just build it 'they will not come.'
Learn to market by reading and taking on side projects to learn or if you want to focus on coding and building either get a partner who is a great marketing and sales person or outsource it.
The above is a starting point. Thoughts?

@Jumpshot44 +1 for getting a partner.

I'm weary of asking people though, because I don't have money to invest, and we all know what it's like being told, "if you do the work, when it picks up, we'll make loads of money!" Lol

I have a similar issue. I don't know if this will fix it but I plan on creating a weekly group with other coders in the same boat. We will work on our own projects or group projects and hope to eventually catch the interest of someone wanting something built. We plan to market ourselves as a dev team. Just a start but if you surround yourself with positive people usually some good comes out of it.