-When at the start of the final Boss level, quickly activate your jetpack and fly straight up as high as possible. You will see a blimp that has "Duf beer" written on its side. Shoot the blimp with your RPG or Devastator and a large amount of items that include medipacks and ammunition will fall out.
-If you have a jet pack, fly up and destroy the beer blimp. Guns and health will scatter on the ground, allowing the final Boss to be killed easier. Use the Devastater for best results.