Surely there’s nothing wrong with it, right? A customer in a restaurant with self-service fountain drinks asks the cashier for a water cup. A small (maybe 9 oz.), translucent cup is handed to the 
“customer,” so that he can dispense some drinking water into his free water cup. The customer then makes his way to the dispenser and proceeds to make another selection. He might fill his cup with Sprite, because it’s the “same color” as water and maybe no one will notice. Or he might be bold enough to just go for the Coke or even the red power drink in his “free water cup.”
In the grand scheme of things, someone might say, “What’s the big deal about a little cup? They charge three dollars for regular size! They can afford to let some go!” To ask for a cup to “use for water,” knowing that it will not be used for water, is lying (Col. 3:19; Prov. 6:16-19). To dispense a drink other than water into a “free water cup” is stealing (Eph. 4:28; Ex. 20:15).
Some might think they can “outsmart the system,” but can you “outsmart” God?