How does my dad spend $500 every night when he goes out and gets drunk?!
Drinks at a bar vary in price depending on where you live. Some cities are more expensive than others. But he's probably paying $3 for a beer, or $5-$6 for a mixed drink (depending on how complicated it is).
If he's spending $500 a night, then he must be buying drinks for other people too.
Drinks are expensive so he could be blowing it all on himself and/or other people. i.e buying rounds or drinks for everyone. Since he's drunk he could be giving his card to pay the bartender and they might be helping themselves to an extra hefty tip.
Alcohol isn't cheap. Bad beer might be but liquor is costly. He could also be buying drinks for his friends which will add up.
He goes and buys a bunch of teddy bears to give to you someday. Only explanation.
pays for a hooker