You could use either structure. The language is flexible that way. I assume it's the same in most languages. The first examples are actually statements..."you can't swim." but if you add the question mark you turn it into a question. If you were speaking then the last word is spoken at a slightly higher pitch, which turns it into a question. Also, for native speakers (in all languages I assume), we tend to abbreviate and contract our sentences to speed things up. I find this to be a very difficult thing when I try listening to French. "Do you like Chinese food?"....is a perfectly formed question. "You like Chinese food?"....is a contraction, but if you say the last word at a higher pitch it's understood to be a question. "Ya like Chinese?"...is almost slang language. We're so lazy we change "you" to "ya" because it's slightly easier to say, I guess. We don't add the word "food" at the end because it's understood that we are talking about food. If we were talking about the people we would ask..."Ya like the Chinese?".

We tend to use both of these structures in English. The more commonly used form is that using question words. When we make a statement into a question, there is more of a sense of another emotion being expressed - whether scepticism, or surprise, or joy. It depends on the context. We don't use that form nearly as much, though, so don't overuse it.

Both structures are fine and equally heard. The first group ('You like Chinese food' and 'You can't swim') is just more casual.