I can't say I swear by anything because all I have right now is a cup holder insert that allows me to put larger cups in it. It blocks the climate controls and the drips from the cups get on the buttons and all around the console.
Having said that, my targeted ads lately have shown me stuff like this:
https://stupidcartray.com/collections/all-products-1
I cannot speak to the quality or effectiveness of these, but I've been considering trying one. I usually have an empty passenger's seat since my wife's car is our family car. If I do get one, I'll come back and let you know what I think of it.