I don't think it's possible to scare yourself on purpose. [You can scare yourself on accident like seeing your reflection in a mirror when you suddenly turn around in a dark creepy room to just see it there but ON PURPOSE no... ]

Laugh? Well I suppose that is a way that could possibly disrupt the rhythm the hiccups but I can't just make myself laugh. If I were to try it would be forced and fake since there's nothing to laugh about.