I found a way to make them without explosives on youtube out of a water balloon. It was hard and they were sensitive but you could give it a shot. I'm not sure how well they work, I've never used them. I use the ones with small firecrackers.
Does water work?
milsimlabs.com
i bought some, they arent perfect but they get the job done. Also AI (Airsoft Innovations) came out with a really cool one. I think
the water baloons ones suck do not even bother they are completely unreliable most of the time they burst in your pocket or as you are making them...just get some m-90s wrap it in a paper towel and pour bbs into the paper towel its the best way
By "explosives" do you mean fire works or fire crackers, because I've read something about making claymores out of party popper's I'll be glad to find the link for you.
Deep Fire and Airsoft Innovations both make airsoft safe, green/red gas powered, grenades. Despite how this is going to sound, spend the money or forget about homemade designs. Ive tried them all. Balloon style is crap on the field, easter egg grenades using firecrackers work ok, but they are still not super effective, and can be very dangerous. I saw a person try to throw one back this past weekend at a game, and it exploded 3 ft. above his head, i also saw one that detonated and sparked a small fire on the course we were on.