I've been wanting to post this since last summer, when I learned it in a parent-child class, but then time went by and it didn't seem a very wintery sort of craft to post about. Now a year has passed and it's summer again. Where does the time go?!
All you need is a plastic water bottle and tape or markers to decorate it. The plastic bottle must have a cap. Oh and the grown up uses some sort of awl, nail/hammer, or something else to punch holes in the bottle.
(Note: about plastic bottles, we try to avoid buying them, but if you do have any lying around or find any as trash, it feels better to give them a second life as a craft project before recycling them.)
Have your child decorate the bottle as s/he sees fit.
Then you, grown up, use an awl, or nail and hammer, to punch holes in it either at random or in a pattern.
After that, fill the bottle with water and put the cap on. Take it outside. When your child starts to unscrew the cap, the water will flow out of the holes. This makes a great science experiment too for the little ones: what happens if you unscrew it part way? all the way?