So then you never worked in a restaurant and been asked which course or meal the people are eating ... because a common reply is "The soup course" or "He/She is eating the soup still". And i agree the THE is flexible in most context in english, but here clearly says 'die Suppe', "the soup".
Wasn't it supposed to be 'drink'?
because you can't "eat" liquid food.
You move the soup from the bowl to your mouth with a spoon. That counts as "eating" in German and, in my experience, in English as well.
Drinking is through a straw or by raising the container to your lips.
Simply because that's what the sentence means. It doesn't really matter whether they "eat soup" or "drink soup", because what's important is the fact that you are ingesting soup; how you do it is not important. It's true that the difference between eat and drink is how you ingest the food, but no-one really cares how you ingest your solids and liquids and so the distinction has come down to that you eat a solid but drink a liquid. Hence, what you do to soup depends on whether you consider it solid (eat) or liquid (drink)…
(just so you know, I disagree that you either eat or drink soup, I think you slurp soup.)
I can't give you specific rules, but from studying French for many years I know that other languages do not follow the same rules as English. Sometimes articles such as "the" are used even though the sentence could/should be translated without the direct translation of the article. Most of the time translations will be made in context. You have to remind yourself that English is a language derived from both Germanic and the "Romance" languages. (Spanish, French, Latin, etc.)
So in the end, in daily usage in German (I am not asking directly about the question, as it is a practice for what we have learnt), Do german people prefer to say that "they eat the soup" or that "they drink the soup" or do they have a different way of saying it? I am just asking the most natural and normal way they say it. What is it?
Because den is masculine accusative, but Suppe is not masculine -- it's feminine. So you need the feminine accusative article, which is die.
(Only masculine words have a distinct accusative form in German; for feminine, neuter, and plural words, the accusative looks like the nominative.)
Why isnt it "is eating"?
Because the two words "is eating" are not a correct translation for the complete sentence Sie isst die Suppe.
What was your entire answer? Did you, for example, type "She is eating soup"?
(There are accepted translations that include the words "is eating".)
How can one eat the soup?
With a spoon.
What is the difference between Juice or Soup?
Juice is usually squeezed from a fruit or made by pureeing a vegetable (e.g. carrots). It's usually drunk (out of a cup).
Soup is usually eaten from a bowl with a spoon. It can have many different ingredients -- even fruit, e.g. blueberry soup ( https://en.wikipedia.org/wiki/Bl%C3%A5b%C3%A4rssoppa ).
There are also cold soups, e.g. gazpacho. They're still eaten with a spoon, rather than being drunk out of a cup.