Theory: Vim is also Shroob Sustenance

Abstract
In addition to using Vim as a fuel source for their saucers, the Shroobs also use Vim for their own sustenance.

Arguments

 * Argument 1: During the battle with the Elder Princess Shroob, sometimes Shroob saucers will come in and deliver her a glass with an unspecified green liquid that she uses to heal herself. These glasses are identical in appearance to the glass of Vim that Swiggler drinks from before transforming the Vim into saucer fuel.


 * Argument 1: Vim is described as the Toads' "mushroom power" by Toadiko and appears to contain the souls of Toads. Shroobs, being mushroom-like creatures themselves, may consume Vim because Toads are close to them in physiology in this way.


 * Argument 1: Inside the Shroob Mothership, Shroobs are shown bathing in a viscous green liquid, many with their heads under said liquid. This liquid may be Vim.