Another one that has been around since the dawn of time, or at least since foreign language classrooms came into being!
For homework, give the students a list of vocabulary to memorise, and test them on it when they come back to class.
You could do this with a list of vocabulary from the lesson you’re setting the homework in (revise today’s words!) or set it as prep homework (learn next week’s words to make the lesson easier!)
I like the prep idea, as I think that it gives the learning more meaning than “just another test”. Students who do their homework will get an immediate, noticeable benefit in their next lesson, and with any luck this will encourage them to keep on top of their vocab. Of course, the flipside of this may be that students who ignore their homework will become lost in the lesson more easily. It will be a judgement call for you based on your individual class and requirements.
How else can you put a twist on a vocab test?