I have never gotten hiccups by eating fries at McDonald's. I only get hiccups when I've either drank something or eaten something really fast. The hiccups come from that.
Oddly, taking a sip of a carbonated beverage - like a soda - stops my hiccups 9 times out of 10. It's weird for me because the carbonation is a gas but someone explained that this is because the gas fills up the air in your stomach that you just sucked in when you ate or drank really fast.