I remember when they were all the rage, back in the '80s, but I've never personally owned one. My parents had one when I was a teenager, and Mom mainly used it to suck up bugs, when she saw them crawling across the kitchen floor. She saw that as preferable to stomping them and then cleaning up bug guts. I tried using it to vacuum my car, but found it very unsatisfactory for that purpose. The nozzle was too big to get into tight spaces and the suction power, well, let's just say it sucked. As happens with those things, the built-in, non-replaceable battery eventually gave up the ghost, and Dad opted not to replace it.
As I've been writing this, I realized I do have a cheapo, made in China, 12v Dustbuster-like contraption that plugs into the cigarette lighter socket in the car. It's in generic, holiday-themed packaging, so it must have been a Christmas gift at some point, but I have no idea who gave it to me, nor do I remember the last time I actually used it. As I recall, it did little besides make a lot of noise.
These days, if I need to use a handheld vac, my go-to is one of my Royal Prince 501's, or an Oreck BB, if I need a hose. The latter is pretty much ideal for my cars.