I’m glad you asked. Actually that is not accurate. The truth is Panera is more like a coffee house cafeteria. You don’t have the server coming up to serve you and depending on your tip. You order your food at the counter. And the coffee is free all day all you have to do is order one cup of coffee and you can refill it as much as you want. I sometimes work remotely and what ever state I am in - if I know a panera is near by - i am confidant i’ll be able to work from there. I prefer this chain over starbucks because starbucks music is often too loud to concentrate and there are no free refills. But to your point - yes you should order something if you are going to study in a coffee house. I’ll get lunch or a pastry or two and of course the coffee. If you are not going to order anything at all it really is not polite to study in a coffee shop - in that case your default should be a library.

Edit - Consider the cafeteria too at ikea! Once again - its a cafeteria. Bottomless coffee. Only issue is bathroom is far from the cafeteria. No one will kick you out. Spacious area - nice view of the city.