How does soap work to kill germs? Viruses are a self-assembled nanoparticle in which the weakest link is the lipid (fatty) bilayer. Soap dissolves the fat membrane and the virus falls apart like a house of cards and dies. 

How does sanitiser work to kill germs? Alcohol Based Products which pretty much includes all “disinfectant” products, contain a high-percentage alcohol solution (typically 60-80% ethanol) and kill viruses in a similar fashion. 

When soap is available it is the superior choice, but it is always wise to keep sanitiser with you when you don't have access to soap and water.