Hmm, here is a mildly dumb idea.
Go gamble on something with a 50% chance of success where you can choose when to stop playing and if you want to play again.
Then, start by betting $1. If you win, quit. If you lose, bet $2.
If you win then, quit. If you lose then, bet $4.
So, just continue betting $1+ (what you lost before) until you win.
This makes it very likely that you will come out with a spare dollar, and the only reason you won't come out with a spare dollar is if you run out of money. which is possible but unlikely.
This is why I said it is a mildly dumb idea.
(BTW, don't do this if its illegal.(obviously) I don't know all the laws on gambling)
This might not be good for getting cash, but if you go to IDK Vegas? this is probably the best gambling to do.