Long ago I designed and printed a 5cm level 3 Menger sponge: https://www.thingiverse.com/thing:3459
. This was first printed on a Stratasys Dimension uPrint with dissolvable support material.
Now, despite the long horizontal bridges, I find I can reprint this sans support material on my MK2S by first rotating the cube so it is "corner up" by rotating in x by 45 degrees and then in y by 35.426 degrees, then configuring Prusa Slic3r to add supports for the first 100-150 layers, to hold the cube up on its point.
This photo shows two half-cubes and a full cube printed in Prusa silver PLA, a 2.5cm cube printed in Hatchbox white PLA, and an "anti-cube" (the L3 Menger holes) printed in Hatchbox clear PLA.
The up-facing sides of the cubes are very nice, and particularly in silver, have an attractive sheen. The down-facing sides and interiors, printed with a severe overhang, are a bit rough in places, particularly corners/edges, but are still acceptable.
Also, with the 2.5 cm cube, with small holes of approx. 0.9 mm, most of these holes are open and I can see clear through the 2.5 cm of layers of material, even though the many layers were deposited at a non-perpendicular angle to the holes. I think that is remarkable layer-to-layer registration for a home-built device.