ah, Dalmatian. Lol= PERSISTENT breed. (poor you lol)
dals are such a lean boney breed the plastic beds are prob not a great idea (plus they will prob just chew/eat those as well lol) but beside the costs of replacing beds and the mess, digestion health issues are scary too, so I hope this helps
if you use a spray like Bitter-Yuck No Chew Spray, be sure to use outside, wear junky clothes and with gloves on, its friggan nasty, an a beatch to wash off, or there is bitter apple spray or natural route of hot sauce but some Dals dont get phased by this stuff and actually like the vinegar in these. If you buy them, try a small area with the dog to see the reaction, if not a deterrent return the stuff.
If they are just out door dogs you could go a more natural route and think out of the box with me for a min
make a dirt doggy house.
Make a dog house with high door lip and L shape (I will draw an example and attach it in a few...too bad I dont have my schematics program an more, so you will have to guess the # of feet/inches that best fit your yard)
buy fine grain sand and fill it.
The sand is a fab coolant/insulator appropriate for the weather changes, they can dig and adjust placement till they are comfy.
just replace the sand as needed (and check reg for sand fleas depending on your climate area)
or if you gave a few days off: dedicate the entire day for a few days to only the dogs training.
watch the dogs all day long and every time they start on the bed use horn distraction with a growl and bearing your teeth than when they stop messing with bed be all happy and play with them. remove the bedding at night when your not there to supervise behavior...every time they mess with it/all day long/ for at least 2 days being sure to follow up every moment you can afterwards to reitifey the rule.
oh I almost forgot....are they male? neutured?