It is a shortened word for what happens when you have a hangover. You have booze-anxiety..."bangs". You feel uneasy about what you have done and said and are pretty sure you are in trouble with someone somewhere.
Dude, I went out hard last night and then woke up with a bad case of the bangs!
Sauce is an action word that describes when someone has just taken a sip of a beverage and a friend makes them laugh at that exact same moment and the beverage is then spit back out creating a very fine spittle sauce. This usually happens while friends are enjoying food at a table; thus the term 'sauce'.
Aimee was telling me the funniest story about something that happened to her while she was on holiday right when I took a fresh sip of my mojito; I sauced all over the table!