What is the important element for sensory bottle? Should it contains water and beads or i can improvise?

It is easy to make with endless number of possibilities and creations. Using different materials, babies could easily be entertained and pick up different associations. They are also suitable for all ages (see this article for some ideas which are related to science for the older children: http://littlebinsforlittlehands.com/5-easy-science-discovery-bottles/) There is really no harm in trying to make one to introduce to your child. Just make sure to seal the cap properly to prevent any “accidents” from happening. :)