Low Hanging Fruit

Question for the Word Wardens, the Text Tyrants, the Syntax Superintendents, the Grammar Guardians:

The word "Fruit", what is its plural?

• We say Fruit Juice, not Fruits Juice, even if there is multiple fruit in it. 
• But it is the 'Fruits of our labor', not the Fruit of our labor. Even if there is only one outcome from the effort.
• It is Fruit of the Loom, not Fruits of the Loom. But the do come in multiples in the pack.
• If a plant fruits, it produces fruit, rarely do you see different produce on the same plant.
• They say be fruitful and multiply, with the expectation that many will be produced.

So is fruit an uncountable noun? We go to the market to buy fruit, even if we mean oranges, apples, and cherries. 

So what say you Dictionary Despots...