I've used beer knots in 15mm webbing, which is almost indistinguishable from 9/16". But they are a LOT harder to tie than in 1" webbing -- I use a knitting needle or something similar to push the webbing down inside the outer tube. Don't expect to do normal 9/16" beer knots in the field.
I use beer knots for 10' webbing slings that I never plan to untie; the slings get used for emergency harnesses, "comfort straps" to lend a hand, and quick loops over boulders for removable anchors. Beer knots have more strength than water knots. Partly it's a gimmick to keep people from borrowing my webbing loops and removing the knot. Other than that kind of use, they are a PITA. If you are tying rap slings on the spot, just use water knots.