I agree with Dachary's comment, but would add a note about the comfort. I would submit that, with the exclusion of our time spent in Kansas, riding in the sidecar may actually be *more* comfortable than home.
At home they lay on the floor. It is carpeted, but it's not "cushiony" by any stretch of the imagination. In the sidecar they sit on a full length flat cushion that's half standard couch-type foam and half memory-foam. They are in the shade thanks to the cover, with a breeze blowing past them.
I put it to you that every dog I know would choose to sit on a memory-foam mattress in the shade with a cool breeze over a carpeted floor.
They're not sitting on the standard Ural sidecar seat. That would be very uncomfortable to them for any length of time. As for exercise... They get walked about six times a day when on the road, vs 3 times a day at home. Given, a bunch of those are short, but again, every dog I know will take 6 walks over 3 even if some of them are short.
If the smells aren't particularly interesting to them they curl up (we have many boring pictures of them curled up together in the tub while we ride) and sleep. Ben sleeps most of the time we're riding, and gets up alertly whenever we stop. Dido's too damn excited about the smells and only sleeps about half of the time.
As for routine, I totally agree, but see no reason a dog's routine can't be changed. It happens every time a dog's owner changes homes. I've never met a dog who was particularly concerned with eating the same food every day. I'm sure there are some neurotic beasts out there who do, but ours do not. As long as they look and act healthy, and what comes out the back end looks healthy, I think they'll be ok with whatever food gets offered. If anything it just makes them happier to eat "real" food.