Shipping soda bottles with contents is expensive because of the weight of the package. And USPS does not allow shipping glass soda bottles by mail. But if you are really keen on doing so, here are a few tips.
Purchase boxes that are designed for shipping bottles, such as a wine bottle box. Go to your local wine or soda shops to see if they have any boxes you can have. If there are none available, and regular shipping cardboard boxes will do.
Get some packing tape and bubble wrap or packing peanuts. They will be used to cushion the bottles against any movement.
Wrap the bottles in bubble wrap and arrange them in the box making sure that they snugly packed. Fill any gaps between bottles with packing peanuts. There should be no room between bottles to minimize movement.
Close the box, secure with tape, and address it.
Take the box to your local delivery services counters, such as UPS, FedEx, or DHL.