In the fourth episode, a coffee cup made its appearance at Westeros for which HBO issued an apology. Then, in the fifth episode, Jamie's actual hand featured in a promo still which the makers said was not part of the show. Now, in the sixth and final episode, plastic water bottles can be seen in the scene where Tyrion decides who should be the next king.
One was spotted near Samwell Tarly's chair and other near Ser Davos. Needless to say, Twitter had a field day pointing out the blooper.