Exercise cannot tighten your loose skin, but you can minimize the amount of loose skin you have. If you have excess skin, patience is key as you wait for your skin to adjust to your new size.
A Pepsi takes between 30 and 45 minutes to freeze solid, depending on the temperature it was at before putting it in a typical home freezer. Be aware that most (but not all) Pepsi containers will burst if you keep them frozen for more than 2 hours.
The Pepsi didn't freeze over a whole weekend and my the beer is still in the back seat waiting for a birthday bash on March 13. I did finally cover the beer with my shearling coat until then, though! Your 2 liter bottles won't burst. They may freeze at some point, but even at 20 degrees, I have my doubts.