Location: I live in the Villiage of Hyannis in the Town of Barnstable in the Commonwealth of MA
Posts: 2,795
If the cooler only had fish for a couple days then it should not be that bad and a simple cleaning with simple green (environmentally friendly) and at worst an overnight soak should do the trick.
If the stink got baked into the cooler as in open in the heat you might be screwed. I am another that thinks the bleach is good for a rinse but I would not let the bleach soak into the cooler as it does remain and I do not want my fish having a slight odor of bleach. I will second the softscrub with bleach as this seems to leave less of an odor then straight bleach.
Also, check out your local bait shop and see if you can get some "bubble gum". This stuff is great.
"It is impossible to complain and to achieve at the same time"--Basic Patrick (on a good day)
Buy bleach and mix with water...25% mix will kill anything (including AIDS)and makes everything look spotless. Let sit for a while. I clean everything with it and it is cheap. I wash my entire exterior of my house in that too. After its sits, rinse well and you are goodtogo.