I take a damp cloth and wipe it out but my top doesn't get dirty unless an egg exploded then it can get messy, which hasn't happened to me but did to a friend of mine.
Why not bleach? I've used bleach for years! Half and half solution of water and just bleach. Then I rinse with hot hot water, then cold cold water. No problems yet..I have great hatches!
oh my new incbator is a Hovabator 1602n that i got for 30 and it works!!! still have to clean it though. i thought it was an lg since that was what the seller said it was.
Just my opinion but I think some people get a little carried away with sanitation. I don't use bleach or cleaners in my styrofoam incubators. I only use antibacterial soap. I think that is sufficient for killing the bacteria. Some people put somewhat poopy eggs in there incubators which isn't very sanitary either. I don't wash my eggs but I so take a scotch bright pad and wipe the poop off of the eggs if there is any on them. I do spray Oxine in my incubators and wipe the residue out. It is non-toxic. I also use it in the coops.