I wrote this a few years ago when this came up…
Along with oil=earl, terlit=toilet, abeets=pizza and many others…my little Sicilian grandma also said sang-wich. She was born in Italy, but learned her English in and around NYC. You don’t hear much of this around NY any more, but interestingly, in SE Massachusetts and RI, where there are many Portuguese, I have heard similar pronunciation. Be interesting to see if any one ever figured out the roots of such accents/pronunciation.
I don’t like people using "sangwich" to be cute or different, but for many it was simply the way they said the word.