ZENS -for gods sake, get your Dad off the sugar! Or at least some of it.
He will get insulin resistance, then Type 2 diabetes, not good!
I was a sugar junky for years. He may have adenal burnout, so seeking a rush from sugar. Chinese herbs can fix this, if prescribed by good naturpath.

Stevia is good - I use it in tea and to sweeten small things( it also helps insulin go back to normal, if levels are buggered).
Or I use honey. Still a bit bad but white sugar( or brown or blonde) is just bad. Its killing the barrier reef, too, with nasty washouts from crops over here in Australia too.
Ok enough meddling! No kids and I turn into everyones mother!