Can you explain how in Acts 2, when those spoke and everyone understood in their own language, how they could be accused of being drunk on "new wine"?

Three improbabilities: First, that these mockers would think that getting drunk would enable one to speak about 15 different languages instantly, without years of study abroad. Second, to think that "new wine" (gleukos), unfermented, would cause drunkenness. Third, Peter reminds them it is the third hour, Jewish time, (being 9 a.m. Roman time, the same as ours). This was the hour of the morning sacrifice and it was not usual for men to be drunk at this time. I Thessalonians 5:7 says, "...and they that be drunken are drunken in the night."

For these mockers to make such a statement, they were probably alcoholics themselves. These, no doubt, used the Feast of Pentecost just as some use Christmas as an excuse to "celebrate" and get drunk. These men are proof that Proverbs 20:1 is true. "Wine is a MOCKER, strong drink is raging: and whosoever is deceived thereby is not wise." Wine had perverted their thinking so much they even thought "new wine" (unfermented) would make a person drunk. That’s what alcohol will do to your mind.