https://en.wikipedia.org/wiki/List_of_presidents_of_the_United_States_who_died_in_office

The Zachary Taylor section is probably my favorite, what a strange way to die:

On July 4, 1850, Taylor was known to have consumed copious amounts of ice water, cold milk, green apples, and cherries after attending holiday celebrations and the laying of the cornerstone of the Washington Monument. That same evening, he became severely ill with an unknown digestive ailment.