It's a little known fact that banana slugs are coffee fiends. Rick encountered them trying to sneak drinks from his thermos three days in a row. Here is culprit # 3, who was satisfied with licking the dried coffee on the lip of the lid.
I can only assume that once Starbucks catches wind of this they'll begin an intensive study of the banana slug to see exactly what causes such cravings, and then have that chemical added to our drinking water. If in a few months you find yourself upping your coffee consumption and secreting a protective slime coat, then you'll know I'm right.