It's the worst part of road trips: You're driving along and suddenly your bladder threatens to explode right there in the driver's seat. In such moments of weakness, we've all peed, or worse, somewhere sketchy-into a empty Mountain Dew bottle, on the side of the road with cars, er, whizzing by-but luckily, it remained a secret between you and your copilot. Unfortunately, photogs once again just couldn't leave Britney alone-they snapped her making a barefoot gas-station pit stop. TWICE.