Have you ever use a Aquapod?

 I think that the rocket would get up to 5m and a bit of the water would stay in the bottle.

Have you ever used an Aquapod?

 You would need a 2.25L empty bottle then you need to fill 1/3 of the bottle with water then you need to flip the Aqua pod so it is upside down and you need to connect the bottle to the Aquapod. There is a black rubber that stops the water from escaping.  

 After that, you need to flip it so it can stand up then combine the foot pump with the valve.

 Then you use the foot pump to make air pressure, pump around eight to eleven pumps.

 lastly, pull the string then it goes into the sky and the water pressure goes up and down.

 

Here's a link to a video.