Since bad eggs exploded I would soak in bleach. Some will use their bathtub and dilute the bleach. I set mine in a shallow container that just keeps the water from leaking out the vent holes, dump in bleach until my container runs out, and top off with water. I leave mine over night. Rinse well and then if possible leave it to dry in the sun. There are some things that even bleach does not kill but are killed by simply sunlight. Wipe with vinegar to neutralize any traces of bleach and remove deposits if your in an area with hardwater. Technically bleach dries to a nontoxic salt solution but it seems to have trouble drying out of all the gaps in syrofoam and the bator still gives off fumes for quite awhile if you don't neutralize it. Rinsing off vinegar is optional since it evaporates quickly but it will be ready to go again sooner if you do. Make sure it is completely dry and there is no smell before using.
Between hatches if it wasn't a particularly dirty hatch like lots of blood, I really packed the bator and had tons of chicks hatching, or exploding eggs I will often just wipe with straight vinegar and let dry before setting the next batch. It's best not to go too long without a good cleaning though or you can lose eggs and hatched chicks to infections but since I often hatch small numbers of eggs I don't feel the need to really soak it every time.