There is this other question: Is sulfur a "miracle cure"? But it received zero answers at the time of this posting, so it is not a valid duplicate target. The claim therein also is too broad.
There are several sources that state Methylsulfonylmethane can make hair grow faster.
There is a study published on Biomolecules & Therapeutics' july 2009 issue: The Effect of Methylsulfonylmethane on Hair Growth Promotion of Magnesium Ascorbyl Phosphate for the Treatment of Alopecia widely linked by those sources, but from the title alone it is about the treatment of one medical condition that causes hair loss, not faster hair growth.
There are also other sites that debunk said claim. (sharecare.com)
The claim seems like a smell, but it is widely believed.
I am interested in the claim as stated by human hair enthusiastic sites: That MSM can make human hair grow faster.