We live in a generation where we toss everything away. There are many things that are put into landfills that could be used for something else. Just think of everything you put into the garbage or even recyclables.
One thing I reuse religiously are grocery bags. With 5 cats, it needs a frequent cleaning. Living in close quarters, city dwelling, they are a lifesaver. Another thing are boxes. If I get a shipment from online, I will use the box for storage or use it to mail something elsewhere.
Water bottles seem to be tossed after a single use. Not so in my household. In our state water bottles can be returned for the 5 cents. We reuse the bottles so much the label comes off.
This one may be a bit unorthodox, but using milk jugs as free weights. Filled up it would only be 8lbs, but for cheap weights it can work. Just have to get creative with the usage.
Theres plenty of other options, just think twice before throwing something away.
I hope you enjoy yhe rest of your day,