[p4bl0]

I looked for something similar but with red wine instead of coffee for my PhD thesis. It didn't exist so in the end I just used a scanned stain of red wine and the wallpaper package :).

[JohnHammersley]

There is now a wine stains version too :) https://www.overleaf.com/latex/examples/latex-wine-stains/cd...

(although I like your workaround!)