Polar Bear cooler here also, strapped on back. Always carry bottles, because the beer I like only comes like that. But, keep 'em packed in lots of ice, or separate them like some have said here, so they can't move around much and rub/bang against each other, or you might have less beer to drink when you get to the campsite. That's sad, and dissapointing.
Nothing much better than an ice cold bottle of your favorite ale at the campsite though!