A fluid gel lies somewhere between a gel, a puree, and a sauce. In fact, it is all three of these things.
It is made by combining a flavored base with a shear-thinning (the ability to break down to a fluid state by vigorous agitation, as in a blender, and remain fluid) hydrocolloid such as agar agar or gellan, and allowing it to solidify. The solid gel is then sheared in a blender into a creamy, fluid state, and remains that way. Using agar also allows it to be reheated up to 185F/ 85C before it remelts.
A good example of a fluid gel and shear-thinning is ketchup. Ever wonder how a few good shakes will loosen it up and allow it to flow from the bottle? Well, now you know. You're welcome.
The greatest advantage of this technique is that it allows us to take a thin, highly flavored liquid such as beet juice, and lend it body and viscosity without the use of flavor-diluting starches.
In the end, isn't it really about the flavor?
1 cup (185 g) liquid flavor base
1/2 tsp (2 g) agar
1/8 tsp (.35 g) xanthan
Blend agar and xanthan into base. Place in a saucepan and bring to a boil. Allow to cool until solidified. Place solid gel in a blender and blend until creamy.