It was more like a gratuity afterward...
I was on vacation, standing outside a Starbucks, sipping a coffee in the afternoon sun. This guy approaches my, eying the bulge down my left leg. He says he wants to have public sex with me. I wasn't that interested, but told him I was planning on being at a certain bar that evening.
Sure enough, he shows up at the bar, where I was out on the back patio. He buys me a beer, then drops to his knees, and takes my cock down his throat. About 30 seconds later, he cums. He gets up, thanks me, slips a $100 bill in my pocket, and runs off. I still carry it around in my wallet. I suppose someday I'll drop it in a charity box.