Being in a customer service means you are at customers' service exactly that - 24 hours in a day. You've got to be polite to customers for the entire day, or at least during your shift. Or at least during every minute of face time you have with customers, and especially if customers aren't rude to you.
I totally get it that Sahur is too early a time for some, but it is your amanah towards the job that you've got to do what the job requires you to do - purely because you took up that job, well informed of the nature of the work.
So Aiman and I decided to head to McDonalds for sahur today (something we do every year during Ramadhan, there must be a day when we have those burgers and fries for sahur). There weren't many people at all, and it was about 4.30am. Counter staff was very friendly - explained Sahur menu to us, took our order and completed our transaction.
All these whilst another staff behind here complains non stop and started showing tantrum and knocking appliances loudly etc. LOUDLY. I tend to tell myself that maybe she was tired, she had a bad journey coming to work and 4.30am was a bit too early for her.
But that's it right, you are in customer service. And your shift is at 4.30am. The least you could do is throw tantrum, quietly. I'm sure McDonalds being such a big brand would not subscribe to such behaviours either. A few customers in line were put off by it but thank god for their friendly counter staff.