This tutorial shows you how to model a bottle in Blender

 

2°) Improve the cap

Add a Modifier " the Subdivision Surface "

 

 

On the cap of your bottle: Add any loop  ( ctrl R ) with the wheel of your mouse, you can add several at once

( look at the pictures below)

 

 

 

 

The cap has a nice shape

 

 Tutorial following : Make a bottle (3) improve the bottle