The typical tourist itinerary to Bromo would include the Madakaripura Waterfall on the way back from the volcano. While the guides ask which one to do first, you should come after the volcano visit to wash off all that sand and dust in the cold river.
Getting to this 200m waterfall is quite exciting. From the village market, you get driven into the hiking trail by motorcycle. Hold on tight as it winds through the narrow and not evenly-paved small roads deep into the park and you won't have a helmet.
After getting off the motorcycle shaken and grateful you have survived, you will need to walk a few more kilometres deep into the valley. Don't be so happy yet - you will need the motorcycle again once you are done.
When the watefalls comes into view, the walking path disappears and your guide will tell you to swap into a raincoat and slippers to walk into the river. Both gear are available for sale at a very reasonable price on the spot and I would recommend getting them. You can only access the best areas by walking into the river and passing under the falls.
You will need to climb along a rocky path up to a height where you can see the falls wrap around. You can swim in the small pool and a few were in their suits taking selfies under the falls.