I have glass corners built in with my tiles in the bathroom, I designed this hanger for my sponge. The glass is 7.8 mm in width, I made this thing with 7.9 mm opening, so it should fit snugly. I included my sketch, so if anybody wants to create the same thing with slightly different dimensions - feel free to use it.

The printing page is also included, though I will print the actual thing with 100% infill, this was just a draft.