Please refer the Tips & Notes here.

This one was tricky. Since the original sentence included "the", you'd think that you should include a classifier. I just didn't because it sounded funny in my head. The me, the original sentence should've been:

"This is apple juice"

It's entirely possible that I just don't understand the Vietnamese language well enough. For now, I'm just going to mentally chalk this one up as the original statement being faulty or deceptive.

i think both are acceptable. "Nước ép" is just more specific

• nước = water
• chanh = lemon
• ép = press together or squeeze
• nước chanh = lemon water = lemonade
• nước ép = pressed/squeezed water = juice
• chanh ép = pressed/squeezed lemon
• nước chanh ép = pressed/squeezed lemon water
• nước ép chanh = lemon juice

nước would specify that it's the liquid/juice and not the actual pressed lemon.