I've always found beer foam a tricky thing to do in 3d. This one is the latest but quite a quick study of making beer foam with a help of tyflow. Foam head is a mesh with VrayScatterVolume-material and I scattered a lot of tiny bubbles on the side of that mesh. Then some bigger bubbles on the top and of course some air bubbles inside liquid. I think it came out pretty good for the small effort.