Exactly this. I've heard of (and witnessed) waitresses deliberately adding sugar to my diabetic friend's coffee/tea, even after emphasizing she couldn't have sugar because of her diabetes, and they add real sugar anyway. Fortunately, she doesn't sweeten either, so one sip tells her if it was prepared wrong.  One fat waitress at our regular coffee shop would consistently add sugar to her drink right in front of us and would get super bitchy when called out. One day, we mentioned it to the owner and told him about her health issues and how the waitress' actions were consistently putting friend's life at risk. Apparently she had a history of sabotaging skinny girls' orders (according to other people we'd talked to) and next time we went in, she wasn't there.  That fat bitch should've been fired on the spot for nearly killing one of the restaurant's customers.