Rather than struggle to "make" a bed in the bunk the traditional way with sheets we elected to go with a "RV Sleep System". I have two kinds, a Travasak on my cabover bunk and a RV Superbag system in the rear on our main bed.
Both are essentially sleeping bags, with the difference being removable sheets inside (held in by velcro) that can be taken out for regular washing. They both have a "Summer" and Winter" side, obviously the winter side has more insulation. Either type takes only a few seconds to "make" when you roll out in the morning.
The Travasak may be harder to find, but my local Camping World had some complete sets and spare sheets, we bought another sheet recently. But some say Travasak is discontinued, I don't know for certain.
The RV Superbag (
https://www.rvsuperbag.com) is a a big step up from the Travasak, able to be customized as far as fabric, sizes, sheet thread count, available matching shams, and you can even get it with a ruffle to make it look more "residential". A ruffle not necessary for a cabover bunk, but if you ever wanted to customize your main bed it is available. We added 2 ruffles to ours, so no matter whether we have it flipped to the summer or winter side there is a hanging ruffle.
My wife will never go back to making any of our beds with regular sheets, we even have a second Travasak on our sleeper sofa when we have need of it.
Edit - It appears Camping World now sells what they call the "All Seasons Sleep System", appears to be comparable to the Travasak.
Below is a picture of our main bed RV Superbag: