This unexpectedly popular art on Twitter was conceived as a simple drawing for a popular comic book author. But as always, it turned out to be a good full-fledged art.
Below are the stages of creating the art and the PSD file with all the layers.
Original post: https://www.patreon.com/posts/hot-drinks-48974651
1. I wasn't sure if the author of this character would agree to such a bold plot, so I first drew this sketch and received permission (and strong approval) to finish it

2. Lineart

3. Flat colors. I always add blush, it makes the characters more natural and lively :3

4. Shadows and light I make a separate layer (or rather, I use many layers, but in the end it turns out this picture)

5. This is how the drawing looks after applying a layer with shadows on a flat color

6. Then I added extra shadows in the crevices - under the eyelids, under the hair, and in other places, to better separate some parts from others. And I also painted the lines in colors close to the environment.

7. And of course I added the white liquid so that there was no doubt about what was in the glass =^_^=

8. And in the end, I added highlights, slightly adjusted the shape and colors - and everything is ready!

A PSD file with all the layers, settings, and corrections is available at this link:
https://yadi.sk/d/vL3aPwt2PSpQ7g