cats

Take all the current litter out of the box. Give the box a thorough cleaning, then run some diluted bleach around it. Drain the litterbox and let it air-dry. When the box is completely dry, put it down in it's usual place and put the new "litter" in the box.

If you have multiple cats, you'll need to arrange something where the sick cat is the only one who can access that litterbox (and that the sick cat can't access a second one, either).

Check with the vet; many times you can refrigerate a urine sample overnight if necessary, but it may depend on what time the lab stops by their office to pick up samples.

If all else fails, you can bring the cat to the vet for them to collect a urine sample. This may entail then keeping the cat in a cage and periodically checking the litter there; or (more likely) the vet will insert a needle into the cat's bladder and draw a sample directly. For obvious reasons, cats tend to dislike this second option.

What we did was in the morning we cleaned all the litter out of the box and replaced it with the stuff in the bag. Then every 30 min or so we checked if he had peed. Once he did pee we collected it and dropped it off then filled the box back up with litter.

I want to add that if kitty refuses to go in the weird litter, my vet advised this: Sit in a room with him (this method works better for boys) and have his regular litter and litter box in there, preferably do the bleach decontamination treatment on it first and use fresh litter. Wait for him to start going....and, scoot the collection cup right into the stream to catch the pee. This worked for me. Kitty was the sort to stand tall, so he kind of made it easy to have enough room to maneuver, and the vet said usually when they start going, they don't stop, even if they are a little weirded out by you putting unfamiliar containers around their backsides.

If you don't think he'll let you get back there with the sample cup, you can try to catch it in something sanitary and plastic with a handle, like a measuring cup that will never ever ever see the kitchen again.

You could also try this with multiple puppy pads instead of a litter box.

I've had cats hold their pee all dang day at the vet even being given fluids and the vet techs periodically applying light pressure to the bladder area. But get them in a quiet room with me and let them figure out they're not going anywhere anytime soon, and eventually they will go!

In my experience, if it's a male cat, you can just buy something new and expensive then show it to the cat. The first thing they'll do is piss all over it to claim it as their own.

When I've had to do this in the past, I was fortunate that my vet gave me a tad more guidance than it sounds like you've gotten.

Put that litter in an empty and clean box, and leave it and the cat in a closed room, ideally a bathroom. Check every few hours to see if the cats peed.

When I've had to do this I was able to leave the cat in the bathroom overnight; when things were more time critical in the vet gave me the option to just have them take a urine sample directly from the bladder in the office.

I have something to add to the good advises you received: do a little pile with the katkor, so your cat can scratch in.

When mine doesn't want to pee in, I put his classic litter in the box, a litter bag over it, and the katkor over the bag, but that only works if your cat doesn't pierce the litter bag.

Keep the pee in the fridge if you have to wait before bringing it to the vet.

Put out the litter while you're around to watch the cat? One of my cats loves of piss on clean litter, which would be convenient for this.

I’d presume you put that (out of the package) on top of the litter. If that doesn’t work could remove the litter and just have that in the litter box

Ladel and stealth

Assuming the cat hasn't just gone, you can "manually express" urine by squeezing the bladder. It takes a little practice, but you can do it with all cats that won't murder you for trying.

You can find a lot of guides on youtube on how express a cat's bladder, since kidney issues are quite common. It works on healthy cats too though.

I just locked mine in a room with the litter box with the non-absorbing crystals for a few hours.