The fact that alcohol is forbidden in Islam is a well established fact and no Muslim has any excuse for not knowing it. It is one of the major sins that doom a person to Hell. This prohibition is mentioned in the Holy Book, where Allaah, may He be glorified and exalted, says (interpretation of the meaning): 

“O you who believe! Intoxicants (all kinds of alcoholic drinks), and gambling, and Al‑Ansaab (stone altars for sacrifices to idols etc), and Al‑Azlaam (arrows for seeking luck or decision) are an abomination of Shaytaan’s (Satan’s) handiwork. So avoid (strictly all) that (abomination) in order that you may be successful”

[al-Maa’idah 5:90]

This prohibition is general and applies to all manners of using alcohol, whether in food or in drink. It is not permissible to use it in food or drink in any way whatsoever. 

It says in al-Mawsoo’ah al-Fqhiyyah (25/95): 

The one who cooks meat with alcohol and consumes the juice is to be subjected to the hadd punishment, because the essence of the alcohol is still present. The same applies to making dough with it and eating it. This was stated by the Shaafa’is and Hanbalis. End quote. 

Al-Sarkhasi said in al-Mabsoot (24/25), which is a Hanafi book: 

If he makes dough with flour and alcohol, then bakes it, it is makrooh (i.e., haraam) to eat it, because the flour becomes impure from the alcohol and the impure dough cannot be purified by baking, so it is not permissible to eat it. end quote. 

He also said (24/32): 

If he puts alcohol in the sauce then cooks it, it is not permissible to eat it. This action is not permissible because it is using alcohol like vinegar, and we have explained that this is not allowed. End quote. 

This is very similar to what is mentioned in the question, that alcohol is being used like vinegar. 

So it is not permissible to marinade meat in alcohol or to soak it in it, and it is not permissible to cook with it at all. In that which is permissible there is sufficient and we have no need of that which is forbidden. The Muslim is enjoined to avoid alcohol completely, so we should boycott restaurants that use alcohol as an ingredient in their food and in preparing and cooking food, rather we should advise them and exhort them and warn people against them. 

And Allaah knows best.