Here is a list of all Mao inhibitors, which may cause an adverse reaction with valium: http://en.wikipedia.org/wiki/MAO under the herbal drugs section of the list as it will tell you what foods Maoi's are found in. Also, avoid alcohol, caffeine (as it may antagonize the effects), the herb valerian, and smoking tobacco.
You can ingest apple cider vinegar as well as grapefruit juice while taking Valium. I googled it quite thoroughly and saw no such restrictions. I myself have taken Valium and no doctor said anything about grapefruit juice or any other kind of juice. Just no tough liquor.