So, how do you go about if you want to go dumpster diving? To go on dumpster diving in The Sims 4: Eco Lifestyle, simply find any big dumpster in a city or a neighborhood and left click on it. This opens up a wheel of choices, including an option to go dumpster diving in it.
And that's pretty much all there is to dumpster dive in The Sims 4. When you use this to search for food, items or even furniture, you can get lucky and score a free item, but you won't always find one.
Note that you do need to have the Eco Lifestyle expansion pack installed to be able to dumpster dive in The Sims 4. Without it, the garbidge bins cannot be interacted with in the same way.