You must be looking at second gens. They are good for things like flares, flashlights, 1st aid kits, ratchet straps, work gloves things like that. If I recall from my 2000 a soda can won't quite fit in the compartments opening thickness wise. Being a cyclist I used to use the stretchy net thing to hold water bottles.
There is also under the back seat in the later ones a small storage box that will hold jumper cables and things like that. Some space under the front seats as well. In my 1st gen I keep the jack and tools under the drivers seat(factory location). Under the pass front seat are the 1st aid kit, a couple of old clean towels. Big Mag light.
I have a tool box that I made for my 1st Trooper back in '88 out of old 1"x12" shelf lumber. 12"x12"x distance between rear wheel wells. It has a padlock hasp and handles on the ends. Straps down with web straps to factory tie downs. It doesn't take up much room but serves to hold everything from a small compressor to recovery gear, oil, come along and chains and straps. Amazing what you can fit in it. It's moved from truck to truck since the late '80s an is now back in a 1st gen Trooper where it belongs.