At least in the Catholic church, the Eucharistic ministers usually drink the rest of the wine. And those are usually lay people. Alcoholics would presumably stick to lectoring. Also, most sacristies contain a sacrarium that the excess wine can be poured into. It goes directly into the ground. No sewer pipes or anything.
Consecrated wine can’t be mixed with unconsecrated so the bottle isn’t an option.
I’m fairly sure they don’t…in the last few weeks I heard a radio discussion in which a priest discussed the possible implications for drunken driving by priests from consecrated wine. He made it clear that there are no derogations from using wine, even in the case of a priest with alcohol addiction.
An alcoholic priest is expected to take only the tiniest sips of dilute wine, but it must be wine. It can be very much a problem if the priest receives no treatment and support. (Letting the Eucharistic Ministers consume the last of the cup is fine for Sundays and feasts, but is pretty much of a non-starter for weekday celebrations where the priest may be presiding over congregations of as few as two (or one) persons.
As noted, no one believes that the consecrated wine ceases to have the form (accident in the theology/philosophy used) of wine, including the alcohol.
[ nitpick ]
Generally, the term for alcoholics attempting to maintain control over their lives is “recovering,” not “reformed.” While one might speculate or wrangle over the meanings and intentions of “recover,” “reform” carries a clear moral implication that the alcoholic was bad and has now “reformed,” so it is no longer used in that context.
[ /nitpicl ]
In some churches, they demand that all excess bread and wine be consumed. In others, they have specific procedures for disposing of it.
(My mother used to take care of the lawns and gardens at the local Episcopal church. While she was working, she would bring her dog and let him romp in the fenced-in area. She noticed that the dog always began by running to a particular spot near the back entrance of the church. She could never figure out why until the rector told her that they put the uneaten bread there. And that’s how we ended up with the world’s most blessed dog.)
Having been an (adult) acolyte and chalice-bearer in the Episcopal Church and working with a recovering alcoholic priest, I can say that I and others saw him take communion by intinction. We would also finish the wine left in the chalice (helped by the ushers who were the last of the congregation to recieve). In that church and in my current church, consecrated wine is kept and used at the next Mass.