Continuity mistake: When Ben and Matt are sitting at the construction site drinking a beer, Ben takes a sip of his beer with his right hand in a close up. The next shot shows him holding the beer in his left hand, flicking a cigarette with his right. (01:43:55)
Visible crew/equipment: When Chuckie and his friends show to Will his new car towards the end of the movie, a boom microphone is reflected on the rear window and also on the rearview mirror's steel cladding moving backwards when Matt Damon steps on forward.
Answer: "How do you like those apples" is an expression used to denote triumph, like "told you so" or "put that in your pipe and smoke it". Will just adds his own little humorous twist to it.
Grumpy Scot