Will anything happen if I disconnect the negative battery cable over night?

 

Nope.

 

If you care about it, you'll lose your trip meter. Possibly your radio could reset as well. I've had both happen when disconnecting mine to work on the car for more than a couple hours. Trip meter will drop after only a couple minutes.

 

It could reset the ECU too. But, I didn't think that's what OP was worried about. Good callouts anyways.