Benalish Sleeper

The kicker ability doesn't let you pay a kicker cost more than once.

If a spell's kicker cost was paid, the spell is "kicked."

As Benalish Sleeper's ability resolves, first the player whose turn it is chooses a creature to sacrifice, then each other player in turn order does the same knowing the choices made before them. Then all those creatures are sacrificed simultaneously.

If you kicked it, you may sacrifice Benalish Sleeper itself as its ability resolves. If you control no other creatures, you'll have to sacrifice Benalish Sleeper.