I use the positive pressure sinus rinse twice daily per dr orders along with Ponaris Nasal Emollient I microwave the water to a boil and cool it bef

I use the positive pressure sinus rinse twice daily per dr orders along with Ponaris Nasal Emollient I microwave the water to a boil and cool it before use. I am going on a 4800-mile train trip in the U.S. I will have access to bottled water on the train. How do I sterilize the bottle between uses? I will not have access to a microwave and I dont trust the water on the train. Thanks.