We only stayed at CS for a couple of nights, and didn't get the refillable mugs, but we did eat at the Pepper Market a few times. The Pepper Market is unlike other food courts, in that you go in and get a ticket. You go to the different food stations and get your ticket stamped with what you've eaten. Then, when all is said and done, you pay when you leave.
The mugs were getting filled inside the Pepper Market. Unlike other food courts, you actually had to hand your mug to someone behind the counter to get it filled. Thus, to ensure that you weren't eating a meal while you were there, I would assume that they would stamp your ticket as a mug refill only, which you would still then have to present to the cashier on your way out.
We felt it would be too much of a hassle for the couple of nights that we were there. I do think you can refill you mug by the pool bar also, but I'm not positive.
Diana