Loudly.
Very loudly.
I hate taking them places in the car to be honest. They whine and scream and are rather obnoxious. Ripley is the worst, but they're all pretty bad. Dance at least just whines and leaves the screeching to her brother and sister, but even she is annoying. And nothing I've tried will get them to stop. They get so excited and worked up as they know they're going somewhere exciting. And even if they're not, they might have been, so they might as well let me know how excited they are. The only times they ever really go in the car though is for one of a few things: a park, a visit with a favourite person, or the vet. Or to training. And all of those things (in their minds) are pretty exciting. We don't tend to take them on "just because" car rides. We did try that for a while just to see if it would tone down the noise though, but it didn't.
That said, Dance is a great long distance traveller. Once we're out of the city she knows nothing exciting will be happening any time soon. And I've never taken the Dobes very far (more than an hour), but they're quieter too outside the city. And on their own, Ripley and Dance are pretty good even in the city. Keira pretty much always whines regardlss, but not as loudly on her own at least.