Oh no, what's this noise..?

Spent ten minutes during a ride this week trying to resolve a weird hissing/bubbling sound on the bike. Sounded like it was coming from the brakes, like there was air that was working it's way out of the system. Levers felt fine though, no fluid leaks on levers or calipers. Checked the air spring on the fork, that was good too.

Then realised it was my new Camelbak podium bottle equalising pressure after I'd taken a drink.

My sense of stupidity was outweighed by the sense of relief that it wasn't going to be an expensive fix!