You can pump the cap upward as hard as you can, which is the first easy and rough way.

Twist that head like a soda bottle cap and some of it will pop out in a second.

Open the shower gel, clean out that tube, and do it again as before.

Squeeze the shower gel bottle cap open: rotate the liquid nozzle counterclockwise for about a circle (the cap does not move), the liquid nozzle will automatically pop up, and then press on it.