I saw this on GMA the other day and we tried it last night. It was stated that it is near impossible to chew/swallow 6 saltines in under a minute.
None of my kids or their friends could do it. Make sure everyone has a glass of water, so they can moisten the crackers left in their mouths. They actually tried it several times, changing techniques from one cracker at a time to trying two at a time, still without success!
BTW, my dd works in a restaurant and she has been seeing patrons trying this for months.