Being the sober friend in the crew can come with some pretty annoying disadvantages, like becoming the default designated driver at every boozy social engagement. One sober redditor decided to make it a little better for herself by imposing a “designated driver tax” on her drunk friends whenever they expected her to drive everyone home at the end of the night. She didn't expect anything too crazy–a few sodas here and there, or a covered dinner once in a while–but one friend was positively scand…