This is an example of how to set up a respawnable, explosive crate for multiplayer.
This is achieved by using a func_button with its health value set to 1 to make it shootable, its direction set to down, lip set to -1, its reset delay set to 10, and its speed set to 1000 for the visible crate. The button targets an env_explosion for the actual explosion, and a trigger_relay that targets an ambient_generic with a delay of 10 seconds for the respawning sound.
When the "crate" is shot, it will quickly recess into the floor before triggering the explosion. After 10 seconds, the crate will come back out, allowing it to be shot again.