From what I can see of the menu online, the snack symbol is absent, so my best guess is NO you cannot use snack credits. easywdw.com did an early review when it first opened, and said that they do NOT have a way to refill your mug either. Remember, it's usually a TS restaurant, so they don't have a self-serve drink station. You can refill your mug at Mara and bring it into Sanaa, if you wish.
I have no idea about the snack credits but you do NOT need to go all the way to The Mara to fill your mug, there is a drink station in the Kidani gift shop where you can purchase and refill your mugs.
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