Money in the couch, etc..
As silly as it seems you can start hunting around and find spare change and money in the house and car.

While your at home check in or under every cushion on all of the stuffed and upholstered chairs or sofas in the house.

I once had almost $15.00 on the floor of my car and under the seats.

I used to have a car with an ashtray ( I don't use it - I don't smoke), that had bills and change stuffed into it.

They accumulated from me stashing the change after I paid when I went through a fast food drive through window.

I have found money in clothes pockets from last season and my friend found $40.00 in an old pocketbook. It is a last minute way to rustle up some cash.

I found a small piggy bank from many years ago in a box of mementos that had collectable coins in it.

I used to keep a large mouthed wine bottle on the bookcase to dump spare change in at the end of each day. You might have the equivalent sort of thing.

So make a game of it for yourself and see what you can come up with.