The planet Hoard, Sweet Hoard only contains one level - a boss level. You only have eight levels in order to beat the Trash Monster, but he's not much of a challenge to be honest.
Phase One - Destroy 10 Minions
It's really as simple as it sounds; drive around and pick up weapons to annihilate 10 of the Trash Monster's minions. They are slow and don't have very good aim, so you should complete this phase of the boss without losing any lives.
Phase 2 - Destroy Trash Monster's Thrusters
Every weapon has turned into a grenade pick-up - simply hit his thrusters with these in order to progress the fight. Be sure to avoid his searchlights, otherwise he'll lock onto you and blast you into smithereens. Each time you destroy one of his thrusters, he will become 'mad' and start throwing giant bombs about the map. They're slow and easily avoided by sticking to the outskirts of the map.