Also research NAC [0] supplements. They work as a precursor to glutathione in the liver which is typically depleted during the course of alcohol consumption. Might only be effective for acute effects of alcohol though.

Edit: Also, make sure your friend is consuming coffee [1].

[0] https://en.wikipedia.org/wiki/Acetylcysteine

[1] http://www.journal-of-hepatology.eu/article/S0168-8278(17)30...