Work out what is actually making him sick
Car sickness in dogs is usually one of two problems, and the fix differs. Young dogs often feel genuinely queasy because the balance system is still maturing — they drool, lick their lips, yawn, and vomit on bends. Other dogs feel fine physically but have learned that the car predicts something awful, so anxiety produces the same drooling and sickness before you have left the street. Watch when symptoms start: sickness in the driveway or at the sight of the car points to anxiety; sickness twenty minutes into winding roads points more to motion. Note what you see over a few journeys, because that pattern is exactly what a vet will ask about if you need their help later.
Rebuild the car as a good place, in small steps
Weeks before the holiday, undo the association slowly. Start with the car parked and switched off: let him hop in, scatter treats, play briefly, and get out before any worry builds. Next, engine running but going nowhere. Then a two-minute drive around the block ending back at home with something he loves, and only when he is relaxed at that stage, short trips to a favourite walk. Keep sessions frequent and boringly successful rather than heroic. If he vomits or panics at any stage, the next session goes back a step, not forward — pushing through sickness teaches him the car really is as bad as he feared, and undoes the work.
Set up the travelling conditions that reduce nausea
On the day, small physical details matter. Travel him before a meal or several hours after a light one, because a full stomach makes vomiting likelier. Keep the car cool with a window cracked or air flowing toward him, since heat and stuffiness worsen queasiness. Secure him where he can lie down and brace — a crate or a harness in the back seat — and where he can see out or settle facing forward, as a dog sliding around in the boot feels every bend twice. Avoid strong air fresheners, drive bends and braking gently, and plan breaks every couple of hours for air, water, and a toilet walk before sickness has a chance to build.
Know when practice is not enough and the vet comes in
If several weeks of gradual work still leave him vomiting, trembling, or miserable, book a vet appointment well before the holiday rather than hoping the big day goes differently. The vet can check for ear problems or other causes, talk through whether his sickness is motion or anxiety, and discuss options that may help him travel comfortably — a conversation that needs your notes on when symptoms start and what you have tried. Do not borrow remedies from other owners or give him anything from your own cupboard; what suits another dog, or a person, may be unsafe for him. A trial run on a medium journey after that vet visit tells you whether the plan works before the holiday itself is at stake.
Protect the holiday plan with a fallback
Build the trip around the dog you have, not the one you hoped practice would produce. Plan shorter driving days, stops he will enjoy, and accommodation where an unsettled first evening is manageable. If, despite everything, he remains a wretched traveller, weigh the kind option honestly: a trusted sitter at home may give him a better week than hundreds of miles of nausea, and that is a legitimate answer to this question rather than a failure. Whatever you decide, recording his car-sickness history, what helped, and the vet's advice in his KinsLe Pet Passport keeps that hard-won knowledge ready for the next journey and the next vet who asks.