Hi Johnna ---
Slider foods can be anything that you can eat more than a handful and never feel in your pouch. Several foods become slider foods when you combine liquid with them such as graham crackers and coffee. But also mashed potatoes and gravy or even an unmeasured portion of "healthy" yogurt. More solid foods --- protein --- have better staying power in your pouch and if you follow liquid restrictions they will not slide through. Though some may disagree, I even consider oatmeal a slider because it just doesn't stay with me.
Hope this helps. Here is the link to the 5DPT FAQ's which addresses slider foods and liquid restrictions.
5 Day Pouch Test FAQs