Is it okay to open full Powerade bottles and then close them after 15 seconds or so? Then drink them weeks l8r?

Alright, today is the day that you can get double points for the "My Coke Rewards" thing, and our family has a huge stash of Powerade down in the basement. I wanted to know if it would be harmful or have any effect to the Powerade if I opened them, looked at the bottom of the cap for the MCR code, and then tightly screwed the cap back on. Thanks!