This will make sims wanna clean it even more! DO NOT LET 'EM! Another valid option is fence around the trash, or hide it somewhere. PROGRESS! This should happen in several hours.
If you've got neat sims, watch them! After some time ( 1/ 2 of a day), trash will start to terribly smell. Wait and Watch Trash needs some time, 'till turning into a plant. Leave litter/garbage/trash on ground and dont clean it up! Make sure other sims won't take out the trash! 2. You also can use cheats, testingcheats true, then bb.showhiddenobjects and search trash. Get Trash There are many ways obtaining trash, both with cheat, and without cheats! One way is fixing stuff, and leave trash at outside grass/sand, another way is kicking trash can. As I was browsing, I saw, that lots of you need help with the Trash Fruit.