A theory, when you plant a live grenade into someone and leave right away (via a door nearby, or maybe even fast travel), and then you come back, the NPC will still be alive and the live grenade will have dissappear from their inventory. I suppose from this method, you can give grenades to NPC's. Just plant a live grenade, then simply give them as many normal grenades as you want, and leave the area before it explodes.

Not sure about this one. Gonna test it out right now