Doing a Google search for "beet air", it seems to be a foamy, bubbly substance made of just beet juice and soy lecithin (to stabilize the bubbles) made with a hand blender.
These photos are not Disney-related:
Here is a photo of salt air (saltwater and soy lecithin) on a frozen drink:
This photo has beet air somewhere in it, not sure which one it is (am guessing the left backmost one):
That's what I was going to say. Marcel in season two always did foams, and then when he did a special episode in season three he served foam tableside, LOL.