Any standard salt you have in your kitchen will work.
Salt lowers the freezing temperature of water and makes the ice colder. It may take longer for your bottles to freeze depending on the size of your freezer.
Spread the bottles out so they don’t block any of the fan’s airstream. Put the bottles on a small table in front of a standing fan. Don’t use the oscillation setting on your fan if it has one. Keep it pointed at the water bottles for the whole time.
Keep multiple bottles prepared in your freezer so you don’t have to wait for them to freeze again.
Be careful when handling a utility knife.
Alternatively, use a soldering gun to melt the holes through the plastic.
Tie one bottle on each side of the motor compartment of the fan.
The fan will pull the cold air from the bottles through the holes you drilled. Since the bottles are attached to the fan, you can use the oscillating feature if your fan has one.
