Dirt /sludge / hard junk in my fuel tank

I pulled my front tank out, and my fuel pump is shot , so i know i need a new one. The tank is dirty as well , with good (or bad i guess) amounts of sludge on the bottom (truck has sat up for a while), and some harder residue / junk all through the tank, but i don't think any rust. Is there a product that i can use to help loosen all the crud? Something i can pour in and let set? Then dump out? Or how else can i do this? Can't afford a new tank right now.