What is the necessary action after waiting five minutes during canteen treatment?

After waiting five minutes during canteen treatment, the necessary action is to screw on the canteen cap and shake. This step is critical because it ensures that the disinfectant or treatment solution that was added to the canteen properly mixes with the water. Shaking the canteen enhances the effectiveness of the treatment by distributing the disinfectant throughout the water, allowing for a more thorough disinfection process.

This practice is essential for ensuring that any harmful pathogens present in the water are effectively neutralized, making the water safe for consumption. Following this step, it will be appropriate to let the treated water sit for the required time to ensure that the disinfection process has adequate time to work before the water is consumed.