Alright, so you wanna make an inexpensive pressure bomb without messing with drano and sulfuric acid and all those other dangerous chemicals.(which can burn the crap out of your skin if your not careful.) All you need is a battery, a 2 liter plastic bottle, and hydrogen peroxide(3% by solution is fine), a hammer and a sharp nail. The size of the battery doesn't matter, although I don't recommend some of the D batteries because the new ones aren't dry cell anymore, and the concentrated sulfuric acid inside can burn you.
First, you might want to move everything outside, cause if you don't know what you're doing this can make a mess. Take the battery that you're using, I prefer a duracel or energizer AA battery, and set it up vertical, so the negative side is facing towards you.(That's the flat side to those who don't have a clue of what I'm talking about) Now, while holding the battery with one hand, take the nail and place it on the center of the negative side of the battery with the point of the nail against the battery. With the hand that it holding battery, you should also hold the nail in place. Gently, and I mean gently, tap the nail with the hammer until a tiny hole is in the battery. BE CAREFUL WHILE DOING THIS!!!!!!! Batteries are under pressure from the chemical reaction that takes place in them, so move your head to the side, you don't want to get sprayed! A little air should spray out of the battery, this is good, you just relieved the pressure and now the battery is basically harmless. Now, however you can get the battery open is your choice, I prefer using a hacksaw and sawing it lengthwise, but whatever you want to do. Once it's open, you will see a whole lot of black stuff and a rolled up piece of paper in the middle with silver chunks of metal. The black stuff is Magnesium Oxide, this is what you want to collect.(The silver stuff is Zinc) Use the nail to scrape it from the battery, never your hands. It contains a small amount of Sulfuric Acid in it, not enough to harm you, but some people react to things different than other people. If you have gloves, use them!!! Once you have all the "Black Stuff" from the battery, let it sit for about an hour in the sun or under a light, this will dry it out. Once dry, crush it into very fine granules so there are no chunks. (You don't have to let it dry, but the bomb will be better if you crush it up.) Alright! You're almost done, all you have to do now is pour 2 16oz. bottles of Hydrogen Peroxide(they sell for about 25 cents at Walmart) in the 2 liter bottle and add the "Black Stuff!" Viola!! there's your bomb! When you add the Magnesium Oxide, screw the cap on as fast as you can, make sure it's tight, real tight, throw it and run! You should have a very nice explosion in about 10-20 seconds!
This method is tried and true, works everytime, if you do it like I said. Be careful though, I am not taking any responsibility for your behavior! You do what you want with this information!