Oh yes you can! You may have already done so as a kid and just forgot. All you need to do is turn on a garden hose, stand with your back to the sun, then adjust the hose's nozzle so the water comes out in a fine spray. Look closely – a rainbow will appear in the spray [source: Rao].
If you'd rather create a rainbow via a more official science experiment, gather a shallow pan, water, white paper and mirror. Fill the pan half-full with water, then set the mirror in the pan at an angle. Head outside (it has to be a sunny day) and adjust the pan so that the sunlight hits the portion of the mirror that's submerged in the water. Take your white piece of paper and hold it above the mirror, moving it to different angles until, magically, a rainbow appears on the paper. Only cloudy skies in your neck of the woods? Use a flashlight to replace the sun [source: Merali].