[It] boils down to a simple breathing exercise. First, exhale completely, then inhale a deep breath. Wait 10 seconds, then—without exhaling—inhale a little more. Wait another five seconds, then top up the breath again. Finally, exhale.~ Uri Bram from, https://www.theatlantic.com/ideas/archive/2023/02/scientific-hiccup-cures-hiccaway-straw-ssmi-breathing/673151/
Sometimes I straight-up do public service announcements. Here, have a cure for hiccups!
If you’ve thought about how proper breathing works, you’ll quickly realize those instructions involve incrementally, increasingly flexing your diaphragm muscle. (If that isn’t obvious, the Thoracic diaphragm page on Wikipedia has you covered.) The muscle spasm is part of a feedback loop involving two of our nerves, and intentionally activating the muscle breaks that feedback. The trick is that you need to really flex it… flex it much harder than you normally do when breathing.
Note that if you do the “hold your breath” part of the exercise by closing your glottis (what’s that?) and relaxing your diaphragm, you’re doing it wrong. The entire point of the exercise is to flex, flex, flex and hold tension in the diaphragm muscle.