Question

IS IT A SIN TO DRINK WINE?

Answer 1

This is region/religion related like in the US the Mormons.

For Christians, No, Jesus turned water in wine. Water was an integral part of temple ceremony and was lavishly used during sacrifice. Also Water Into Wine miracle narrative itself records there were six stone jars full of water present there just to be used in ceremonial washing. That is how much water they had. There is no contemporary record showing that water was scarce. After all, Jerusalem was supposed to be a land flowing with milk and honey.

So doesn't it seem counter-productive to turn water into wine? Wouldn't it actually be more characteristic/benevolent to turn wine into water?

No. Wine was an integral part of Jewish marriage custom at the time. Not providing sufficient wine was an insult to the guests and thereby a shame to the newly wed. Jesus helping them in their need is in fact a "characteristic/benevolent" act.

Was it all just to show off his superpowers and that's seen as more impressive?

Have you read the Gospel narrative? Vast majority of people who attended the wedding including the master of the banquet did not know where the wine came from. So your claim of show off his superpowers doesn't hold good.