In some places the passenger can be charged with a DUI if they are intoxicated enough and have a beer can or other alcohol in their hand and are drinking it when the car is pulled over.
However if the passenger is just drunk and has no alcohol on them and you get pulled over they will not be charged with any crime.
Police in most places want the drunk person to be driven home and not driving so you cannot or should not get arrested simply for being drunk in the passenger seat.
That is unless you tried to do something to the officer while drunk then you can be charged with that offense.
But the passenger should not be drinking any alcohol while riding with you because you can get charged with an open container crime.