<p>I want to print out a flat object without any support structure straight onto the build plate of my ender 5. It's going to be PLA and I need it to be thin enough to still be flexible.</p>
<p>I don't have a picture available, but imagine that I wanted to print out the Coke Cola and then wrap it around a bland soda can, so that the logo is raised up slightly?</p>
<p>Alternatively, what is the best layer height to use, and how many layers should I use?</p>

With PLA you can just heat it to curve around the object. I've done this with up to 2mm. Real easy with 1mm.
I haven't tried thicker but assume it would work ok.
You'd have to glue it though to make it stick. My attempts were just to shape the prints, I didn't want them sticking so I shaped them around a glass bottle.
If you want it flexible in it's own right, then I suggest 2 * 0.2mm layers. I have a large 2 layer print in front of me that bends easily.
This can be rolled up into a tube, but as soon as you let go it will return to flat.
1 layer is even more flexible but tears along the lines with a bit of effort. So if you want it really flexible I suggest you print 1 layer at slightly lower than normal nozzle height to really get the lines melded together. Or a bit hotter than normal.