Squeeze out guts into the petri dish and squirt lightly with plain saline. Tease out the tubules and view under high power on a dissecting microscope. Female crickets are usually full of eggs that look like yellow rice. Male crickets tend to be smaller and are easier to assess. Dispose of CPR and other chemical inhibitors as directed by your institution's safety office.
Plain saline can go down the sink.
This is a subjective measurement and therefore is a little tricky. You may want to decide in advance which sample you predict will show the most uptake and arbitrarily assign that sample a maximal value. You should also consider whether the person making the assessment should know which test solution was used. This experiment is a good place to introduce students to the concept of blind and double-blind experiments. To create a double blind experiment, the instructor can provide solutions identified only by a number or letter.