I have had good luck with the plastic liter or bigger size water bottles. Fill the bottle about half way up with water. Add about a tablespoon of the lye drain cleaner. Shake or swirl the bottle until the lye disolves. Remember, now that the lye is mixed in with the water you want to keep it out of your eyes and preferably off your skin.
Aluminum foil is the easiest to use.
Put them into the bottle. Try to get them in so most of the aluminum is in the water. In several minutes you should see some bubbles collecting on the aluminum. After a few more minutes the hydrogen will start rising to the top. Don't over do it with the lye.