Alcohol causes muscles to relax more, including those found in your throat.
As your muscles in your throat surrounding your upper airway over relax, they push against you airway reducing the size and restricting airflow.
Air from breathing as you sleep still needs to rush in and out, but now through a much narrower air passage.
The air speeds up and soft tissues found in your throat and mouth vibrates and causes the sound that we know as snoring.
Poke and push the snorer onto their side, which causes the airway to get a little more space causing less vibrating tissue and, therefore, noise.
Stick in some special snore barrier earplugs.
Sleep in another room.
Stop them drinking so much.
Get to bed well before they get to bed and try and get some undisturbed sleep.