It is the verb, which dictates the case of the following noun. Many (not all... )
very common verbs, like "mieć", "widzieć", "jeść", "lubić", "kochać", go with the accusative. What is "done" to the noun here is that you "have it". It is a good idea to practice any new verb together with the noun in its respective case:
to have (who(m)? what? - Accusative) - mieć (kogo? co? - Biernik)
I have (what?) a sandwich/sandwiches - Mam (kogo? co?) kanapkę/kanapki
I can see (what?) a house/houses - Widzę (kogo? co?) dom/domy
I eat (what?) an apple/apples - Jem (kogo? co?) jabłko/jabłka
I know that 'some' has a variety of functions in English - or, to put it another way, a variety of translations into Polish - but as a native speaker of English I can tell you that
"I have a sandwich and fruit" "I have a sandwich and some fruit"
... mean exactly the same thing. There's not reason to not allow what TonyKreuch suggests.
Excellent. It's a tough one, because you could probably find example of English sentences where adding a 'some' changes the meaning somewhat, but then there are lots of cases where it makes zero difference. At the same time this is only a side issue to teaching Polish... so a hard balance to keep.
Isn't it cute?
The first word means "warzywa" (vegetables) in Polish (potatoes, beets).
The second one means "owoce" (fruit) in Polish (apples, grapes, oranges).
If it helps to straighten out your eyes, there are "pomidory" (tomatoes),
known as vegetables, but they are... fruit, so you can call them "owoce".