The staff of the Sonic I went to were very nice and informative. I ask about "dedicated" fryers. Although they had 3 fryers, I was told that their Breaded Cheese Sticks were also fried in one dedicated to only potatoes. So, you just have to be bold and ask and if still in doubt, don't get it. I don't think a lot of fast food places are aware of cross contamination...in fact, that is a problem even in restaurants who claim things are gluten-free.