Zira Grover's ceremonial cup

On her limousine on the way to the Cave of the Gargoyle, Zira Miranda Grover and her guests had drinks served to them by the Empress' servants. Zira had a priceless goblet filled with butterbeer, which she forced Summer to drink.

Thomas Carter
During his enslavement, it is likely Thomas Carter was forced to drink from Zira's cup as well. He would have been forced against Zira and made to open his mouth, after which Zira would pour the liquid down his beautiful throat.

Summer Petersen
Zira made sure not to have any physical contact with the cup until she offered it to Summer. For her part, the veteran's perception of the drink itself is a great mystery. She was also not given a choice as to what she drank.