A clean glass

Two Jewish men, Mr Cohen and Mr Abrahams sit down in a smart kosher restaurant and a snooty waiter comes over to take their order.
"Sirs what can I get you?" enquires the waiter.
"A glass of orange juice," says Mr Cohen.
"A glass of orange juice for me too" says Mr Abrahams, "but please make sure the glass is clean."
The waiter stalks off in a disagreeable manner, and eventually comes back with two glasses of orange juice.
"So," he then inquires, "which one of you wanted the clean glass?"

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