Often get kids with hiccups in school.
Take a fiver out, wave it in front of them - tell 'em it's theirs, if they hiccup "NOW". "Come on I'm waiting." "NOW!" " "Come on, you'll lose that five pounds!" ........ Work the moment

, until the thought occurs to them to try a fake hiccup. And put the fiver back in your pocket. They're all having a giggle by now.
And in ten minutes time? As the student if they've still got the hiccups? Guaranteed answer - "No sir". Amazed faces all round

. Never yet had to pay out!