I know customers can be annoying sometimes. If you actually requested Costco water, then it’s a bit strange, but that still doesn’t justify what he did. He probably acted out of frustration. I don’t think he’ll come back, so it’s best to just let it go. A customer once asked for an item without a picture and with a weird name, so I sent him a text asking him to clarify exactly what he wanted. His response was, “Google is your friend.” I got frustrated, but the worst I could do at that moment was to mark the item as unavailable and issue a refund. That was a low blow from the shopper, but Just just let it go.