Just in case this isn't a joke thread, ...
It's not fungus, it's calcium deposits. Use CLR or Lime-Away mixed with water. Shake it up, remove the cap & let it sit a few minutes OUTSIDE, then rinse it out with water. Repeat if necessary.
I'd just throw the damn bottle away (in a trash can, with no liquid inside) & go get a wide-based Gatorade or one of those half gallon juice jugs from the grocery store.