I have a friend in New Jersey who is 18 and on probation for possession of marijuana with intent to distribute. He got on probation while he was 17. He was just arrested for underage drinking. He was in a car with another friend who got pulled over the driver was arrested for possession of marijuana (under a gram) and my friend was drunk and arrested as well. He has a previous underage drinking citation as well. In terms of violating his probation what is he looking at as punishment? More probation? Jail?

Probably jail, depending on the mood of the Court.

It would appear that probation didn't keep him straight and the Court may decide something more drastic is necessary.

The issues I see

First arrest was drug related and related to sell ( more seroius)

This arrest, there was drugs in the car ( in GA he could have been charged with that also.) and the probation hearing will know and most likely mention this.

I would say at least some jail time