If you havent already heard of discovery bottles they are a very cheap, simple and quick make that children love. Here's a link on the Imagination Tree's website, which is a brilliant website full of great ideas to get creative with kids.
I have to be honest and say that Eloise just loved making it and they didn't get played with that much afterwards but even for the fun of making them it was worth it.
Eloise loved looking through and choosing individual bits for her bottle including sequins, buttons and ribbons. She then put them into an old but clean plastic bottle, filled it with water and I glued the lid on. Voila all finished.
We ended up with pink water from adding a pink ribbon but I think it makes them look even better so you could even add some food colouring to yours!