What is the plural of "passion fruit"? [duplicate]

Your example sentence is fine. The plural of fruit is fruits. You are confused over the matter of countable and uncountable nouns.

This is tricky to explain, because there are few strict rules about which nouns are countable and uncountable, so I will hope you will forgive this over-simplified account:

• Some nouns (e.g. chair) are countable. We can say "one chair", "two chairs", etc. They have singular and plural forms.
• Other nouns are uncountable. We do not say "one fun" "two funs". There is no plural form of fun.
• Many nouns have both countable and uncountable senses. E.g. you can have a bar of chocolate [uncountable], or a box of chocolates [countable, plural].
• Nouns for classes of foodstuff (fruit, meat, cheese, etc.) are usually uncountable, but they take a countable sense when we talk about different varieties (a wide selection of cold meats and cheeses).

Your example sentence talks about different varieties of fruit, so fruits is fine.

If you want to talk about two apples and an orange, you would not use fruits, but pieces of fruit.

John ate three pieces of fruit; he must have been hungry.

If you want to talk about different kinds of fruit, you use fruits:

John's three favorite fruits are apples, bananas, and papayas.

If you want to say John ate two orange segments and a quarter of an apple, you can say

John ate three fruit pieces

(not pieces of pieces of fruit).