A:One should abstain from restaurants that serve alcohol or that sell Haraam foods, even if one is only consuming vegetables or coffee.
As for alcohol, Rasulullah (Sallallaahu alayhi wa Sallam) said: “He who believes in Allah and the Last Day shall not sit at a table on which wine is served.” (Narrated by Imams Ahmad and Bayhaqi) This means that it is Haraam to be in an eating place where wine is served.
If a thing is doubtful then according to Hadeeth, we are instructed to refrain from it. Indulgence in doubtful things will eventually lead to indulgence in Haraam. This is mentioned in a Hadeeth in Tirmidhi.
Moulana Yusuf Laher