So, I just moved into a furnished apartment. The apartment comes with a mattress that's entirely plastic on the outside. I got my fitted sheet on it just fine. But, the fitted sheet slides everywhere on the mattress since there's no cotton-to-cotton friction.
How do I stop my sheets from doing that? To be clear, my sheet stays on the mattress just great. It just slides around all over the place.
Try clips, or pins, on either end of a short piece of cord or elastic. Try a cord length of about 1-1/2 feet. Make four.
Attach one of these across each of the four corners of the bottom sheet selvage about 1 foot from the corner to reach diagonally. This will increase the amount of "tuck" under each of the corners to hold the bottom sheet from slipping in any direction.
This will create a "fitted sheet" on steroids. It'll be a lot more secure with these between the mattress and the box-spring or bed stretcher.
They're easy to remove and replace when you want to change the sheets
If you're handy with a sewing machine, make a fully enclosed mattress cover - needs to be stretchy material, with a zip, so it fits tightly over the mattress, like this one available here
https://www.amazon.co.uk/Velfont-Towelling-Enclosed-Mattress-Encasement/dp/B00E3S6AA4
Otherwise just buy one, but that wouldn't count as a hack!
Since it is staying on, but I'm guessing you mean the top is sliding around, you need some sort of frictional surface between the sheet and mattress.
I have this foam grippy stuff that I usually see marketed as cupboard liners. You can find all sorts of sizes. I would put a layer of that down. It will grip the plastic and give the sheet something to grab onto. It is also soft so you shouldn't even know it's there.
Here is a link to what I'm talking about, you might have some of this or something similar around your home. "Duck Select Grip Easy Non-Adhesive Shelf Liner, 12-Inch x 20-feet Taupe ", found on Amazon
You could also use some rubber strips if you have them, it just needs to have a lot of friction to keep the sheet still.
....just put a jersey (or flannel in the winter) fitted sheet on (that has lots of elastic) to hold it down and put it on before you put your regular fitted sheet on.
I haven't tried this but try to put a whole heap of double sided sticky tape on the plastic mattress (this is if the plastic of the mattress is thick enough so if you remove it it won't damage the mattress). Then put your bed sheet on and try and see if it works.
