What you drink could be used to trace your movements.
From the link:
The bottled water, soda pop, or micro brew-beer that you drank in Pittsburgh, Dallas, Denver or 30 other American cities contains a natural chemical imprint related to geographic location. When you consume these beverage you may leave a chemical imprint in your hair that could be used to track your travels over time, a new study suggests. The findings, believed to be the first concerted effort to describe the use of beverages as a potential tool to investigate the geographic location of people, appears in ACS’ Journal of Agricultural and Food Chemistry.
A person who drinks a beer or soda in Denver, Des Moines, or Dallas, for instance, consumes a different isotope signature than a person in Las Cruces, Las Vegas, or Laramie. The finding may help trace the origin of drinks or help criminal investigators identify the geographic travels of crime suspects and other individuals through analysis of hair strands, the study suggests.