It is generally agreed that students focus more on a particular structure during either written or oral practice when the context is either very funny, very interesting or personalised. The first two can be quite difficult to create, as what one student finds interesting or funny, another won't, but personalisation is easy.
One very easy variation on having students fill in a sentence with an example of a structure being studied is to write a series of sentences which are unfinished. The students may have guidelines on the structure to use when completing the sentence, but none whatsoever on the content of the sentence. The whole idea is that they come up with something from their own experience, the mental effort needed to do this helping consolidate the structure being used in their memories. Here is an example :
1. The funniest thing I've ever seen is __________________________
2. The tallest person in my family is __________________________
3. The scariest film I've ever seen is __________________________
4. For me, the most difficult part of English is __________________________
5. The worst moment of my life was __________________________