Shower gel is much more harmful to the environment than bar soap because of the surfactants and so on. That's why I bought soap bags made of sisal, which also have a rubbing effect. The disadvantage is that they dry extremely slowly and so everything gets a bit slippery if you use them in the gym, for example (I know that "slippery" is not an adjective, but I think you know exactly what I mean). Could you make soap bags like this from the recycled material you use for the vegetable bags?