Apples and Carrots -A Weird Juice Combination

I don't think that's weird at all, if you mix sweeter apples and carrots. I have had carrots, cucumbers, tomatoes, beet, and cabbage. All blended for some vegetable juice. They don't taste sweet, by the way. Also I've tried fruity-veggie combo. Some vendors sell them, telling of their health benefits. That may or may not be the case, however. It's sometimes nice to check around something that may be considered unusual once in a while.

1 green apple is already sour so it's not surprising that 1 carrot cannot sweeten 3 green apples.

Some 'vegetables' go surprisingly well with 'fruits'. Strawberries and cucumber are an example. When you think about it, a cucumber is closely related to melon, though it doesn't have the sweetness of melon, so it works very well in combination with a sweet fruit like strawberry, in fact strawberries, slices of cucumber and a sprig of mint are standard additions to a Pimms fruit cup. I once made a fruit compote with blueberries and courgettes (zuccini). The acid in the blueberries was supposed to react with the courgette juice and cause it to gel (which it sort of did). Unfortunately, I've lost the recipe and can't find it on the Internet! Avocado and chocolate blended till smooth also makes an unusual and creamy dessert guaranteed to fool anyone asked to guess what's in it!

I once tried grapes and banana milk shake, it tasted really weird to me

I once had banana's with my Coffee when I was so hungry and have nothing to eat HAHA