The Guinness world record for the tallest stack of M&M’s is 4 and was first achieved by Italian Silvio Sabba on 21 December 2016 and later by Brendan Kelbie in 2020. – WTF Fun Facts
Source: https://www.guinnessworldrecords.com/world-records/94349-tallest-stack-of-mms
2021 UPDATE : Will Cutbill broke the record by stacking 5
Guinness World Records is a pay to win scam