Authorities say 19-year-old Marvin Washington Jr. was arrested Wednesday and charged with malicious tampering with food.
Greenville County investigators say surveillance video caught Washington leaning over the cups before he filled them Saturday at the Simpsonville restaurant. Authorities say the customers discovered phlegm when they removed the lids of the drinks to add more sugar because the iced tea still was not sweet enough.
The owner of the McDonald's says he follows stringent food safety procedures and asked people not to reach conclusions until all the facts come out.
It wasn't immediately clear Wednesday if Washington had a lawyer.