Shiny Objects Making
Where To Start
First, you should fast travel to this location in Goo Lagoon.
You will find yourself in a cave with Gary in front of you. Immediately turn around and exit to the giant sandcastle.
Once you exit the cave, you will be standing at the end of this bridge facing the castle.
All you need to do is walk into the closest Thunder Tiki to make it start storming.
Once it starts to thunder, move off of the bridge to not get hit by the explosion and punch the Ham-Mer robot.
The second you defeat the robot, launch a cruise missile to the top of the sandcastle next to you.
All you have to do is hit any of the red Thunder Tikis at the top. Once everything has blown up your money total will have been 665 if you got them all in the same combo or 705 if there was a gap between the two. You can choose to wait a couple of seconds between each group of tikis if you want that extra 40 from the second combo bonus.
A way you could space out the combos to get both bonuses is to bubble bowl or cruise missile the robot duplicator off the side of the bridge and get an extra 50 shiny objects in the process, bringing the total up to 755 per trip.
The last step is to cross the bridge, go back into the cave, and exit again.
You could also jump off of the bridge and bubble bounce to fall faster into the goo below as it seems to have a checkpoint on the bridge, but only if you entered from the cave. It will not spawn you there if you went to that spot from any other location. (Spawn point was told to me by BizarreMonstrous and I tested it. Works great and will definitely save you some time.)
Just repeat this as many times as you need to and you can get the most money in the quickest way that I have found.