Firebase Cloud Functions - event.data read special value

I´m currently learning to use cloud functions from firebase and just have the following problem:

In my database the structure I´ll be referring to looks like that:

• fruits
  • RandomFruitID
    • fruitID: RandomFruitID

In my index.js I want to create the function:

    exports.newFruit = functions.database.ref("fruits").onWrite(event => {
    (...)

    // INSIDE HERE I WANT TO ACCESS THE "fruitID" VALUE, MEANING THE "RandomFruitID"
    });

How can I achieve that?

Best wishes

via ktm125