In my playing days prior to undertaking counting (very recently) I have won at the table side bets with other players who were mouthing about a wrong play someone made. I have always carried one of the little gift shop variety basic strategy charts in my pocket so the bet decider was on hand.
One time I recall was over splitting nines. A player was arguing that you don't split nines against a nine. I said, "you may not, but basic strategy says you do." He argued. I laid a c note on the table rail and said put your money where your mouth is and we'll get a basic strategy chart to decide the winner. He plopped up the $100.
The other deal with an identical bet was over hitting a soft 18 against a dealer ten. Another hundred in my pocket. Goodness knows it was probably more than I won any other way that night.
There have been others from time to time and some are willing to put up some money. If they won't go for a large, I ask just how certain they are and offer to reduce the bet. Some have. Some have not. More often than not they just slink back into their stool.
I may not do those things anymore since I am trying to count, but back then it was just easy money.