Carrier Ready
No matter how much your think you will be traveling, getting your pet used to their carrier is a must!
I made the mistake of letting this slip with our first cat. She was an adorable soft ball of fluff until you tried to put her in a carrier. That is when the claws came out.
Lesson learned?
Start getting your cats used to being in a carrier as soon as possible. When we looked there wasn't really that much info and so we ended up using information that we had found for small dogs. And that is what we built up from. Honestly, I think that what it comes down to is paying attention to the animals needs. Don't lock them in the trunk for ten hours. Make regular stops, give them a chance to drink and use the littler box. Now there is a lot more info out there. For one you can look into crate training, there are places out there with some thoughful instructions.
Make regular stops, but make sure that you keep your pets in the carrier during drive time. Letting them roam the cabin while you drive is just a recipe for disater, and you are putting your pet and your own life in risk, not to mention anyone else that may be envolved in an accident. Never open the car door unless the cat is secured in his carrier or they are on a leash.
For this to work leash training is important.
Don't be surprised if he just doesn't want to use the litter box at all. Cats are finicky about eating and toileting and when stressed will often not do either.
But, as any cat owner should know, cat canot go with out drinkig (most choose to get their fluid from their food).
Yet, even though it is not good for them to refuse eating, refuse a chance to use the litter box, many will. Traveling for a cat, as it is for some of us, is a very stressful experience. Don't be surprised when they act stressed out and elect to hold it. Some people elect to use a covered litter box, the leave it in the backseat. Whenever they stop they offer their pet a chance to use it, as well as water. Another option that you may opt for is to place a puppy pad in the carrier, if you are worried that there could be an accident this is the best option..
As far as forcing their cats to drink. But unless you have tried this, pouring a cap full of water in your cat's mouth is probably not a viable soluton and it will just give your cat more reason to feel stressed.
A better solution would be to use a carrier attachment that allows you to offer them a source of water and maybe just a little bit of food.
Good luck.