Update (8/12): Looks like the glitch has been fixed on PC.
Original story: Though it sounds as if it may have already been patched out on console, there's currently a glitch in GTA Online on PC that will let you fill your pockets with casino chips quickly and easily. The glitch allows players to win the maximum payout on an Inside Track race while only risking a couple of hundred chips.
Seeing as how this is basically an exploit, I won't explain how to actually do it, but you can find it pretty quickly if you search the internet. It doesn't require any bots or scripts: it's just about using your mouse in a certain way when placing your bet.
Be warned: We don't know if or how Rockstar will punish players for using this exploit, but you could be risking having your account banned or losing all those chips if you get busted. And it's probably not worth it, honestly, to win a bunch of fake money while you sit in a casino, though I myself have been doing it a bunch today because I'm a filthy cheater.
The exploit only works with the Single Event betting option, not the Main Event (multiplayer) races. Essentially, you start the race having bet only 200 chips, but while the race is running your bet continues increasing, even though you can't see it happening. If you lose, you just lose the 200 you bet before the race started. If you win, you win whatever the maximum payout is. I just tried it this morning and it's definitely still working.
The smart thing to do is not risk your account by using this exploit. But if you do use it, then the smart thing to do is to bet on the #1 horse, which always has the best chance of winning. The payout won't be massive if the odds are evens or 3/1, but you'll win more often than not. With even odds you'll get 20,000 chips with each win and only lose 200 if your horse doesn't finish first.
Or, you could do what I do, which is bet on the #6 horse which usually has odds somewhere between 20/1 or 30/1. You won't win often and you'll be losing 200 each race, but when the #6 horse does win the payout is huge. I just won 270,000 on a 26/1 horse. It's a big payday for a lousy cheat like me.
I'll let you know if Rockstar takes away my ill-gotten winnings somehow. Proceed at your own risk for now.