The problem of sudden death extends beyond an accident or intoxication; what about all those people who die in their sleep, or in plane crashes, or in natural disasters? Very few of us have the benefit of being able to know that we will die soon, and confess and receive unction.
When Our Lord told us to repent, for we know not the hour or day of the second coming, his words also applied to sudden death: it is important that we go to confession, recieve communion, pray, and be good to our brothers and sisters all our lives, so that should we die suddenly, we will be prepared to face God and answer for our Earthly lives.
Second, should something sudden happen to a good person who has led a Holy life, we not worry about them being thrust into the fires of Hell because of a few unconfessed sins. That is what purgatory is for. We don’t know exactly what is needed to get into Heaven, but we do know that God looks at an individual’s whole life, and most of all, whether they believe and are sorry for their sins.
Lastly, as was said before, there is always time left to repent and believe, right up until the last minute.
However, the matter is complicated by the fact that if one were to die intoxicated behind the wheel, there is a possibilty that an even greater sin is incurred–murder.
Either way, you never can tell. That is why it is important to repent, believe, and lead a righteous life.