In many bar scenes, when the customer/drinker asks for a drink (eg shot of whiskey etc) once it is poured, they ask the barman to 'Leave the bottle' .. meaning they plan on drinking it all/getting rolling drunk etc due to their desperate circumstances.
The pineapple juice is in a carton; so Douglas plans on 'drinking the lot'. I guess that explains it enough?
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Also, please note that sentences can also end in full stops. The exclamation mark can be overused.
Sherlock Holmes 28 March 13:08
Mycroft’s popularity doesn’t surprise me at all. He is, after all, incredibly beautiful, clever and well-dressed. And beautiful. Did I mention that?
--Mark Gatiss
"I know that you believe you understand what you think I said, but I’m not sure you realize that what you heard is not what I meant."
Robert McCloskey