You can use tap water to rinse the rice well. Drain. Put the brown rice in a clean container, and add enough bottled water to cover. Don't cover with a lid.
Cover with a kitchen towel or a piece of gauze, and secure with an elastic band. Leave it in a warm place. Every 8 to 12 hours, rinse the rice quickly and change the water every 1 to 3 days.
I used a yogurt maker set to the lowest temperature setting. I rinsed the rice 12 hours in and changed the water. The rice sprouted in about 24 hours.
I also tried putting the rinsed brown rice in a thermos with 40 °C lukewarm wter. I rinsed the rice and changed the water after 8 to 12 hours. The rice sprouted in 24 to 32 hours.
I also tried my bread machine's "natural yeast fermentation" setting, using the same procedure as for the thermos. The rice sprouted in 32 to 48 hours.
I sprout 2 to 3 rice cooker cups of rice (360 to 540 ml) and turn it into rejuvelac or leaven.
Not all the rice grains will germinate. If about 80% of them have sprouted, it's good.
Addendum: If the rice sprouts too much the flavor will get worse, so if the tiny tip of the sprout pokes out of the grain, it's done.
Story Behind this Recipe
This is a great way to make rejuvelac or leaven, etc., which are indispensable for macrobiotic and other types of "raw" or "living" cooking.
The rice will germinate well at more than 20°C, so keep it warm. Make sure the water does not turn bad, change it frequently. Even at low temperatures, if you wait a while the rice will germinate, so keep the container in an insulated styrofoam box or something and you can sprout the rice even in winter.