Getting stuck without clean water is not ideal. The SteriPen Adventurer Opti UV Water Purifier is a compact device you can take anywhere to get rid of 99.9% of harmful microorganism in any water source. It can disinfect 1 liter of water in 90 seconds. You can also use this gadget as a flashlight.
This UV water purifier works in containers with 1.75″ (di) minimum opening.