Haha, yes about the energy, although I suppose it's not significantly different than arriving at 6am after a 14-16hr redeye and then staying up all day, except it's dark. (Perhaps that does have some meaningful impact on the body's energy). That said, the only reason I'd consider trying this is if I *really* don't want to try to adjust to the local time zone -- for example, if OP is on a mileage run and returning back home.
I don't have any specifics to add about nighttime activities in HK, but I would think killing that amount of time in Macau wouldn't be that difficult. That said, like many places, the available activities would still likely be limited to eating, drinking, gambling, and nookie.
And at least 3 of those 4 you can do in HK.