if you gain control of a players turn can you sacrifice his monsters

[Brian]

if you gain control of a players turn can you sac his monsters

[Void Elemental]

If he/she has an ability allowing you to do so.

[Arix]

You can only make them do things tht they could normally do. Since you can't normally just sacrifice things for no reason, you can't make your opponent do that.

If they have something like a Nantuko Husk in play, you can most definitely sacrifice all their creatures to it. And then conveniently forget to attack with it. And then sacrifice it to itself.