Idiom or word to say to someone who is talking without proof or data

I am working in the IT field. We faced an issue and hired a consultant to resolve that. Consultant gave us some generic recommendation which is not based on any data and will not resolve our issue.

Do you have any word or idiom in English to explain such situation?

Solution 1:

You could say the contractor's recommendations are pulled from a hat, like how a raffle winner might be selected - the recommendation has no rational basis or support, and is seemingly random.

One could also say the contractor is talking out of their ass, which occurs when a person expounds upon a subject with seeming authority, although they don't actually know what they're talking about. Another common term for this is bullshitting.

A way to express the utter uselessness of the recommendation is to remark "that and fifty cents will buy you a cup of coffee". Assuming a cup of coffee costs 50 cents (although not genreally true these days), the suggestion carries no value whatsoever.