The Ligue Nationale de Rugby's discipline and rules commission fined Williams and former Wallabies' star James O'Connor €1500 ($2300) overnight for "behaviour likely to undermine the image and the reputation of rugby".
The duo will also have to attend behavioural awareness training. O'Connor escaped a fine.
"I have given all the evidence, and I think they will understand that I was in the wrong place at the wrong time, so yes, I'm sure it will work out," O'Connor told media outside the hearing.
This month Williams was fined $2300 and convicted of buying cocaine outside a Paris nightclub.
It was also confirmed Paris' Racing 92 fired the 2011 World Cup winner, according to French news site Los Echos.
The Paris club had previously suspended Williams as a precautionary measure and removed him as a club ambassador.
Last month Racing 92 president Jacky Lorenzetti told Midi Olympique magazine that "unfortunately, Ali Williams will soon be dismissed".
Williams has already issued a public apology on social media.
