How do you refill schweppes soda syphon?

To refill a Schweppes soda syphon, first ensure it's empty and clean. Then, fill the syphon with cold water up to the indicated fill line. Next, attach a new CO2 cartridge to the syphon's head until you hear a hissing sound, indicating the gas is being injected. Finally, shake the syphon gently to mix the gas with the water, and it's ready to use.