I have slept in plops a lot and my thick hair never smells sour... as long as you use a clean t-shirt lol.
My hair doesn't tend to dry all the way though I do admit. A little diffusing can be helpful. I also like to use thicker oil sealing type products-Jane Carter Nourish Shine because my hair will sleep out the hold from gel. Idk, but my hair does it. Some people can plop overnight, some people cannot...