I made a great vomiting sound by taking a large bottle of commercial Italian dressing (chilled to make it more viscous) and a gallon juice bottle filled with water. Take the dressing (with the cap on and tip it quickly and hard for the stomach internal sound then in quick succession dump the water on whatever surface you want (sidewalk, toilet etc..) add a little “ughh” on top . You can easily do it all in one, works great! You can even do a few heaves before dumping the water for added realism.
– Genji Siraisi

Soak a sponge in water, give it a little squish to just prevent it from dripping.
Release the water in one big squish over preferred surface or into a toilet.
Mike it from the side, holding the spunge above the microphone level to prevent
picking up to much of the spunge squish itself.
Has a nice dripping tail to it, just like the real thing!
– Giel van Geloven