Actually, beer used to be used for conditioning. It used to have brewers yeast that, supposedly, did benefit the hair. I have heard that the beer they make now doesn't have much of it in it.
I know that many people use them but, personally, I think olive oil and mayonnaise are only good for lubricating the hair shaft. I don't believe that the nutrients in those products are in a form that can be absorbed by the hair.
For the damage we do to our hair now - color, perms, heat styling - the best repair is professional conditioning treatments from companies that study the biology of hair.