I've been using a water bottle that has a strap that goes over the back of your hand (which you can tighten), and I don't actively have to hold onto it while running. It's basically this one on Amazon: http://tinyurl.com/pmpqk7s
I had this question today when I completed Week 6 Day 2 and was supposed to have done a mile in 10 minutes. I did .9 miles. I figured I'd keep going with the program to build up to a half hour run, then repeat that regularly to increase the distance covered in 30 minutes.