Simple to make and fun thing to have,make sure to store all your pyrotechnics,fireworks etc in well sealed containers as air & water can and will quickly eat into unprotected items,These are by no means safe and anything you do with these plan's are and is your own responsibility.
Step 1: Tools Needed.
Aluminum or tin cans many, soda/cola bottle caps the plastic kind, x1 glue gun, x1 Duct tape, x1 strong pair of scissors, Drinking straws, Whatever chemical propellant you decide to use inside, BB's & Flour or both, x1 Firework fuse,visco etc, ,x1 zip lock bag, x1 super glue, x1 appropriate storage/carry container.
Step 2: Construction(1)
Now cover in 3/4 layers of duct tape all the way around make sure the bottle cap is in place at one end and secured in place well,by the tape next grab your straws and cut a small piece off of one cut a hole the size it is into a bottle cap and insert the straw piece,grab your glue gun and fix it in place,this is where the fuse will protrude from the case take the rest of your cans and repeat the process till you have as many as you desire.,now the chassis is nearly finished...next the final part adding your propellant and setting off your device.
Step 3: Final Construction and Testing.
What i did was firstly was collect unused crushed match heads i had previously from my fuse instructable,and used this to power my grenade,added a small amount inside the zip lock baggy along with the fuse,and added a small amount very small amount of glue,to weld the bag closed,then simply stuffed it inside the metal chassis and pushed the fuse through the straw hot glued in place,adding a few BB's,Then i glued with super glue not hot glue the bottle cap the correct way around and left to dry before testing.
Results were okay a small pop and it jumped into the air sending out a nice size burst of flame BBs and smoke.
Step 4: Batch Production
Store them correctly and out of the way of any form or ignition and use them all sooner rather then later.