I reckon that the bees prefer 'drinking' from warm (sunny) wet moss, rather than anything deeper.
But they are certainly attracted to smelly water. Whether its hot tub chemicals or cesspits, the smell certainly seems to raise the bees awareness. And they might even like the taste - as indicating mineralisation.
Putting sugar in the water may not help. It has no smell to help the bees find it, and secondly, if its only weak (did von Frisch say 2%?) its of no interest to the bees - more work than its worth!
Hence I'd suggest flagging up the intended water source with smell rather than sugar ... and making sure its location and presentation are attractive to the bees.