Note to self: Regular attack with non ranged weapons/classes work. Have regular attack when done on a reactor like this cause the close range punch attack instead so it can break it, instead of doing a throw of stars or shoot of bow/gun.

Good catch, and thanks for the note about melee working. That was the clue. Fixed, arriving in the next update: when you attack with a bow, crossbow, claw or gun while standing right next to something breakable, your character now swings the weapon at it instead of shooting past it. That covers the watermelon and also boxes, coconuts and the like. Stand underneath or beside it and attack as usual.