İç is when you command someone to drink. İçer is when you just say that someone drinks
Turkish has no articles. If you wanted to substantiate it you would have to say something like; "Eat the bread" - "Bu ekmeği ye"...Using the accusative ending for the noun "ekmek" which you'll learn in a lesson or so!
When you say that Turkish has no articles, are you referring to this sentence in particular or to Turkish in general?
In general. Turkish uses the accusative to substantiate. In the same way that you might find it in Swedish when you say "finger" for "finger", but "the finger" becomes "fingret". - There's a similar logic here.
There are no articles in the sentence, so I guess we have to take it very literally.