For some explosive fun that you can 3D print at home, I've designed a grenade that's filled with "Party Snaps".
The grenade is composed of three pieces: the plunger, the head, and the body. All three pieces are supplied as individual STLs, so you only need to print what you need when it comes to replacement parts. While you can print and use the grenade at 50%, I recommend you stick with 75% or larger based on my testing.
For instructions and testing results, please view the video at: https://youtu.be/_BEe5IxEdss