system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly are voice cracks?
gpt
Singing is a conscious effort, much like moving around your arms. Holding a note is basically the same as, say, holding up a book with an outstretched arm -- except this time, you are supposed to keep that arm held up at a specific angle. It takes effort to keep that arm steady, but sometimes you would under/overestimate the 'output' of how much effort you put in that and your arm might slightly fall/raise. That fall or raise could result in a voice crack.

Temperature plays a huge part in a singers voice, as do some beverages. Cold water cools your vocal chords too quickly, resulting them in tightening to soon. Milk builds phlegm, which causes you to sound stuffy. Sugary foods/drinks can mess with the lining of your throat.

Source: I've been singing for ten years.