Final answer:
Banquet servers should politely inform guests if a requested beverage is not on the banquet event order and suggest available alternatives. Special requests may be accommodated with manager or host approval in exceptional cases.
Step-by-step explanation:
If banquet guests ask for a beverage not included in the banquet event order (BEO), banquet servers should inform the guest with politeness that the particular beverage is not available per the event's arrangements. If possible, they should offer alternatives that are on the existing BEO. In some cases, with the approval of a manager or the event host, special arrangements can be made to accommodate the guest's request. However, this should be an exception rather than the norm to avoid incurring unexpected costs or disturbing the flow of service.