[BerntR]

I don't think there's a specific sweet spot drill. When you have decent balance and good rhythm and lag pressure through the ball you will find the sweet spot.

Speaking from experience:

Full effort at the driving range often doesn't provide the feedback necessary to detect and correct minor wobbles in the stroke.

The closest you may get is to practice shots inside 80 yards including the short game. Hit the ball with lag pressure and not with back swing length. Pick new targets regularly. You will feel what's going on and you will be severely penalized when you don't hit it pure. So you will become picky about how you address the ball, start the back swing, balance, rhythm, pressure point alignments etc. A lot of the important stuff. If you can pure the ball 50 - 80 yards chances are good that you are very close to what you're searching for also in the full motion. Even if you have swing problems that only appear on full motion it helps to alternate with short game practice to get back on track. It's the best way to learn feel from mechanics. And of course it helps on the score. No wonder the best players in the world spend most time on the short game.