I recently saw on a video post a woman was using the skins from her pineapple to make vinegar, so I decided to do a little bit of research. Some recipes were a little vague, but I found this one to be quite useful, so I decided to run with it.
I used three layers of cheese cloth and used a rubber band around the neck to keep out any pesky bugs. The mixture needs to breathe, so if you put a cover on, it can't. Put it in a dark place and stir it once a day to incorporate oxygen into the brew. Just be careful and remember there's no lid, so don't tip it in a quick grabbing motion or you'll be wearing a nasty brew!
You also need to realize this stuff is going to look like it's rotting in the jar, and it'll turn color before it clears back up again, so don't give up on the mix too soon!
Here's what the jar looks like after around 30 hours sitting in the cabinet when I took it out to stir and incorporate air in. It's definitely starting to have a bit of a vinegary scent, but still overwhelmingly the pineapple does make itself known. Yes, it's supposed to have the nasty foam on the top as it's part of the process, so don't freak when you start seeing it on your jar.