I wouldn't shoot e-waste. This means you have it all over the place after shooting it, making more of a mess.
Go the organic route. The best reactive targets are the live ones, such as squirrels. You eliminate them chewing up your irrigation, bugging your dog, and above all, sustainable. I keep shooting them, and they keep coming back. It's good for the environment and your mental well being.
I don't think shooting batteries would produce the desired effect.
I would use sweet tart candy or sugar cubes or home made bleached flour with water mix then dried or cereal or chalk. No need for clean up and are bio degradable.
They do sell exploding reactive targets but I would be paranoid storing those in the house or transporting them in the car.
HA
How about a fun explosion? Hit ebay for some valve stems and put those old soda bottles to good use. Charged to 100psi, a 16oz bottle makes a pretty good bang. This one has some baby powder in it...
And a 2-liter bottle is seriously impressive...avoid this one if you have persnickety neighbors.