washing up liquid,
bicarbonate of soda.
See through containers/glasses are best and if you are as messy as us you need some newspaper. Half fill the glass with vinegar, add a few drops of washing up liquid and food colouring. Then get your little one to add a teaspoon of bicarb, and watch. This kept my eight year old and four year old amused for quite a while. I have been asked to go and buy more supplies today so they can do it again.