I completed this task on September 6 - October 6, 2014. It was a long month, but I accomplished it. I had given up regular soda back in 2012 anyway, but this was the month that I went 30 days and only drank water or lemonade. Of course, on October 7th, I went straight for a diet soda.
Of course, I have gone back to drinking a diet soda on occasion. The goal was only for a month.