Rat's Saucy Nest

A super simple/basic version of what I do:

I draw the base of the fluid in a darker color of what’s underneath (purple or redish on a multiply layer works well)

I add some highlights in an off white

I add sparkles in a brighter white

Add a soft shadow underneath everything.

Tweak for literal hours until you’re happy.

Done!

For urine it’s pretty much the same, just that everything has a slight yellow-orangish tint. And I work a lot with the luminosity layer with urine, to make it extra sparkly and glittery!

I hope that helped. Also I would look at how other artists draw fluids, and especially how fluids look in real life and then try to incorporate what you saw into your fluids. Try out crazy things and see what works!