Their first clue was when the kid started hitting on the waitress and trying to bum a cigarette.
LOL!
Sippy cup likely one from the restaurant, which means a typical kid cup with plastic top, neither of which are normally transparent. That being the case, I can buy that the parents did not realize the drink being consumed was not apple juice. Since the police found the bottles at Applebees were mislabeled, I do think there is fault on the part of Applebees in this matter. A .10 blood alcohol level is not insignificant for a 15 month old.
Applebees should probably count their blessings the suit is only for 25K.