You can get alot of full size snack items such as boxes of donuts, large bags of chips, cheetos, doritos etc, jars of salsa. I cannot remember seeing 2 liter soda bottles, but if it exsists you will be able to get it with a snack credit.
We were NOT allowed to do this at POP Century in August. There was no label on the shelf identifying the 2-litre of Sprite as a snack, and when I asked, the cm at the register said no. The sprite was around $3.75, if I remember correctly, definitely under $4.00.
I don't remember seeing 2 liter bottles. but we were told(by several cm's) that anything under$4 is a snack. EXCEPT....ready for this..... bananas. Yup. bananas. and we asked several people about that. go figure!