Cleaning the leaves of houseplants with beer – is that useful or harmful?. Use of banana peels, milk or beer to rub the leaves is often recommended online.
This apparently gives the leaf surfaces a nice shine and could replace leaf shine sprays. This treatment is also intended to protect against pest infestations such as spider mites and aphids as well as pathogens. Beer is harmful to the leaves - so is water. Even if the plant shines beautifully after the treatment, this is not a good idea in the long term.