吃 Vs. 喝 in this sentence: 既然敬酒不吃那就吃罚酒
&quot;Drink&quot; is one possible meaning of 吃. From the Taiwan Ministry of Education dictionary definition for 吃
(emphasis added):

口中咀嚼食物後嚥下。有時吸、飲液體亦稱為「吃」。如：「吃飯」、「吃茶」、「吃藥」。

It also has an entry specifically for 吃酒.