Can gulping a very cold drink quickly trigger afib?

Yes: I've seen this before, actually. Sudden cold in the esophagus can trigger extra heart beats (pac's), which then can trigger afib. For people prone to triggered heart arrhythmias, it is important to minimize your exposure to your particular triggers. Common triggers include stress, caffeine, chocolate, alcohol, lack of sleep, sleep apnea, and sometimes sugar or environmental (e.g., cold).