The phrase "like apples and oranges" is commonly used to describe two things that are completely different and cannot be compared. Some synonyms for this phrase include "chalk and cheese", "night and day", "black and white", "fire and water", "oil and water", and "cats and dogs". All of these phrases suggest a stark contrast or complete opposition between two things or ideas. They are often used to emphasize the impossibility of comparing or making sense of two completely different things. So, next time you encounter two unrelated things, you can easily substitute "like apples and oranges" with one of these alternative phrases to add some variety to your language.