What is the most effective use of body slams?
From my experience the best time to use slams is in one of three situations.
When you are about to land on the ground and not bounce off a gummy bear. Slamming in this situations keeps your speed and altitude up so you don't lose as much speed and height which can be a pain to get back.
The second is when you see a large group of gummies on the ground. By slamming into a group you can get more money due to the slam destroying more gummies than just one like a normal bounce would.
The third situation is when you see a special gummy you can use to either speed or get more altitude. If you happen to notice a special gummy and you are above it you can use the slam to hit the special gummy and boost yourself further.