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.
Allow the bottle of water to chill, undisturbed, for about  2-1/2 hours. The exact time needed to supercool the water varies depending on the temperature of your freezer. One way to tell your water is supercooled is to put a bottle of tap water (impure water) into the freezer with the bottle of pure water.