Answer:
Sunk-cost fallacy.
Explanation:
The sunk-cost fallacy refers to the behavior done by the individuals when they continue such behavior because they already invested resources on it (time, money, effort).
In this example, Les invested money on the megaphone of root beer, he starts drinking it but he becomes full, nevertheless he keeps drinking it (even when his friend tells him he will get sick) because he "bought it and not going to waste one drop of it"
Less continues drinking the root beer even though he's already full because he thinks he already invested money on buying it.
Thus, this is an example of the sunk-cost fallacy.
