I know this is 2014 article, but I just saw it and I couldn't find anything more recent. But still is quite telling.

At some stadiums 100% of vendors had major health code violations. Unreal. I'm glad that the parks here in Baltimore were both low.

Example:

Sun Life Stadium
Miami Dolphins, Florida Marlins
Vendors with critical violations: 93%

Inspection report excerpt: In June 2009, an employee complained anonymously that small insects and other debris were blended into frozen alcoholic beverages at a stand where equipment wasn't being cleaned. When inspectors checked, they issued a critical violation for a buildup of slime inside the frozen drinks machine.