This is a cup holder made for NA & NB Miatas. I drink a lot of 16oz cans, which tend to spill everywhere inside the center console of my NB1. The cup holder is designed specifically for cans but you could fit some cups and bottles in too, or adapt the ring yourself to accommodate whatever you like.
I used a modified version of teejay187's four-spoke vent design for my vent piece. They've got a few other vent designs, a very cool race dash, and some other Miata related things. so go check out their page.
First, remove the vent from your car and take it apart. you should have three pieces, the vent ball, a sleeve that it sits in, and a bezel that holds it in place. Then you can test fit the vent portion of the cup holder in the sleeve.
I found E6000 works very well on the PLA I print with, so that's what I used. if you want to do a nice job of this, put the bezel in between the vent and the ring BEFORE you glue. this way, you won't have to break the bezel like I did.
I used some 1" x 1/8" aluminum bar stock bent into this sort of hook shape to act as the base. To install it I used some 3M double sided foam tape. I'm using the scotch brand stuff for mounting photos, which worked fine, but I think their outdoor mounting tape would have been a better option. once it's stuck down, you can drill and screw the hook down for some extra security. I wouldn't trust the tape alone because of the heat cycling and condensation.
Here you can see the cup holder already glued together sitting in the sleeve, and my broken bezel.
I forgot to take a picture before gluing, but it's nothing complicated.
Here's the hook, 1" x 1/8" bar stock, bend it to whatever shape you like. I designed mine to catch the concave portion of the can, which is why it's hook shaped.
The Tape. you can see I've already drilled holes in my hook for screws later, I would recommend doing this before taping.