Sensory bags are great for babies and toddlers. They give them the opportunity to explore and discover using their senses and they are also a great mess free activity which means they are great for taking out and about.
You will need a zip lock bag and some strong tape (I like to use pattened Duct tape) and then you can add things like:
Paint
Shaving foam with paint/glitter/food colouring
water with food colouring/glitter/sparkly confetti
water beads
jelly
coloured rice
water and glitter
For babies who love to stand, you can tape the bags to a door, wall or window.