Possible Clues:

• Hours needed to consume a drink in small amount
• Not much of a drink, doubly hard to swallow it
• Surprise drink at hotel doesn't cost much in old money (3'4)
• Negligible amount a sailor's left within hours
• Hours consuming a drink, a very small amount
• Cry of dismay about what's left? It's a small amount
• As much as is worth a halfpenny
• The Pope imbibes a drink - not much
• So little to buy in a seaside town in two hours
• As much as is sold for a halfpenny