1. The apple of your eye

• Meaning: The person who you are very fond of.
• E.g. She has three children, but her youngest son is the apple of her eye.

2 . Apples and oranges

•  Meaning: To be different from each other.
• E.g. My mom and my mother-in-law are just apples and oranges.

3. The apple never falls far from the tree

• Meaning: To say that “the apple never falls far from the tree” is to suggest that a person’s personality traits are close to those of the person’s parents.
• E.g. Her daughter soon showed her own musical talent, proving that the apple doesn't fall far from the tree.

4. Bad apple (especially US)

• Meaning: a person who is corrupt or wicked
• E.g. It is hoped the inquiry will pick out the bad apples in the police force.

5. Upset the apple cart

• Meaning: To “upset the apple cart” is to ruin plans.
• E.g. Look, he's not trying to upset the apple cart—he just needs to meet later in the day now, that's all.

6. As American as apple pie

• Meaning:  “As American as apple pie” means that something is quint essentially representative of American culture or values.
• E.g. Baseball is as American as apple pie.

Izvor: https://www.eslbuzz.com/20-common-idioms-about-fruits-in-english/