You could use it as an experimental race. Try tactics that you would never dream of using in a race you felt well prepared for, just to see what happens.
Sit right at the back and try for a sprint finish from 1/2 a km out. Go off like stink and try to hang on for as long as possible. Pick a runner and track them. Vary the pace - 1km fast, 1km slow and so on.
I'm running a half marathon on Sunday. I've not done half the training I planned (PB'd in this race last year, wanted to knock more off this year), so all I am going to try to do is a negative split. Because I'm undertrained, it means I'll be going off VERY slow, then trying to take 15 secs a mile off in the second half. If it works, then the next race I'm properly trained for, I'll have the confidence to try it again, but with a quicker first half.
But as the others have said - if you really don't feel like it, there's no harm in just doing your own thing.