IPA: /ˈfoʊmləs/
KK: /ˈfoʊmləs/
Not having any foam or froth on the surface.
The drink was served foamless, making it easier to see the vibrant colors.
Foamless is formed from "foam" (from Old English *fām*, meaning a frothy substance) and "-less" (meaning without). The word "foamless" means without foam or lacking froth.
Think of something that is 'without' ('-less') the frothy substance ('foam') — that's what foamless means.