snake oil 
noun [mass noun] informal, chiefly North American
1A substance with no real medicinal value sold as a remedy for all diseases: some kelp products are snake oil, but the good ones promote plant growth [as modifier]: a snake oil salesman...
- Ever since, unwary Americans have spent untold billions on contemporary versions of snake oil, some of which, like ephedra, have turned out to have few if any benefits and to pose real dangers.
- Maybe his private chemist cooked up an elixir of bathtub gin, snake oil and Smith Brothers cough drops.
- We need good medicine, not more jokey formulas for snake oil.
1.1A product, policy, etc. of little real worth or value that is promoted as the solution to a problem: the new tax plan was denounced as snake oil...
- Promising physical immortality is, simply put, spiritual snake oil.
- They'll serve you much better than some snake oil product.
- In fact, transplanted fetal brain cells have turned out to be, well - snake oil.