If the filler neck opens into the tank near the top center and you can get all of the gas out of it, you might be able to wash it out with soapy water, drain it, rinse it couple of times then run a shop-vac hose down in it and suck all the trash out.

I don't know how yours is made, but if it's like the only buggy I've ever seen with a molded in tank that might work.