Before we get into the pronunciation, can we just all take a second to appreciate the wonder of sherbet? How does adding fruit juice to milk result in something so amazing? Whoever came up with it should have won all the awards, and then had them taken away because they chose a difficult name for their new invention. Though some people can't pronounce it, we can all agree it's delicious.
This one is spelled wrong almost as often as it's spoken wrong. It isn't "sure-bert", like your friend Bert just said something wise. It isn't "sher-bert" either, however much you love those old Austin Powers movies. There's no 'r' at the end of the word, and what you should actually be saying is "sure-bit", like you're dealing with a very confident little piece of data.