"Big and small sandwiches"
Translation:Duże i małe kanapki
It's not "good Polish", but it is sometimes used. I know that ice cream http://www.ice-mastry.pl/sandwich.html is called "sandwich".
I think some places have "sandwicz" in menu. I think it's to distinguish them, as Polish "kanapka" can be open faced. http://sjp.pwn.pl/szukaj/sandwicz.html
Personally I think it would be too much to accept it. It sounds like some corpo-slang (where a lot of English words are used after making just small changes to make them a bit more Polish) and could make lots of people simply surprised and confused.
I agree with Jellei. It is not good Polish, and while people will understand, why learn cases of "sandwicz", when you can learn more commonly used and much less awkward "kanapka".
Why isn't here "duzi" and "mali" used, I thought these were the plural forms?
"duzi" and "mali" are for the 'masculine personal plural'. Sandwiches aren't men, they are objects, so they undergo "not masculine-personal plural". And the forms for that plural are "duże" and "małe".