I think the problem is that it is sometimes quite hard to translate something that does not exist in the same way in another language (locative case).
In "I have (the) sandwiches.", "I" is the subject and the sandwiches are the (accusative) object of the sentence.
In "Sandviçler bende." the sandwiches are the subject, and "I" is the (locative) object.
So I think that the most literal translation would be something like "The sandwiches are with/on/at/in me". (Note that you need the "The" here, because omitting it would make you the place where sandwiches usually are found. Kind of the natural sandwich habitat.)
That is, because if a word is the subject of a sentence, it usually is definitive too, using the article "the" in English.
So I think this is the reason why the sentence has to be translated with "the sandwiches" and not just "sandwiches".
I agree with you.. I also think that "I have sandwiches" is wrong in this case because the phrase "sandviçler bende" can be used mainly as an answer to "sandviçler nerede?" and not "sandviçlerin var mı?".. thus the answer can not be "i have sandwiches" but "I have the sandwiches".. that's at least my viewpoint.. can be wrong, obviously ;)
I think "the" is not in the sentence for this reason. Subjects have a "the" with them but it's not written with the "i" as in objects. (e.g. if sandviçler was object it would have been written as sandviçleri) Sandviçler is a subject here and is understood to be translated as "The sandwiches" and not just sandwiches.
'de' in 'bende' is used for location. so bende is the indicator that the senctence is an answer to 'Sandviçler nerede?'
I think the confusion is bcz the same English sentence is used in different cases, the is context is not given in Duolingo with questions. Just like in many previous lessons we could hardly know if "you" was for Siz or Sen bcz English offers a single word for both of them.
I have sandwiches = Benim sandviçlerim var.
-> lit. "my sandwiches exist" or "there are my sandwiches"
My answer to this was "The sandwiches are mine" and it was marked wrong which is fine. The correct answer given was " The sandwiches are on me". In the "discussion" the correct answer was given is "I have the sandwiches". This is very confusing. As an English teacher these sentences have entirely different meaning.
You cannot use the accusative here. Even though we're trying to say "have," this is actually an is/are-copula sentence. Literally it is something like "the sandwiches are at me." When there is no verb, there is no direct object, and no possibility for the accusative case to show up.
General question for this exercise... In my brain it seems to make more sense to associate "bende/sende/onda/etc" with "is/are with me/you/him/etc" rather than "I/you/him/etc have the (...)" I hope I could explain it clearly. I'm basically wondering what the best translation is. In this particular case for example I wrote "the sandwiches are with me" rather than "I have the sandwiches". It was accepted but I would like to know which is a more accurate translation. Thank you!