> Have a system by which each coffee comes with a unique code on the receipt. This code grants you 1hr on the WiFi before terminating your session.
I went to a place like that a few years ago. I could never comfortably finish my drink within the time limit, so I'd get cut off wifi while still drinking, even if I was just browsing to relax, not spending hours.
Perhaps it worked for them: I stopped going there and taking up seating. Then again I stopped going there to buy anything as well.
The internet time limit was an improvement over their previous policy, of playing music way too loud, which staff told me was deliberate. That didn't actually push people away who had laptops - people like me wore earplugs with noise cancelling headphones over the top, to bring the awful sound down to bearable levels. But it stopped people who came in for a chat with friends from chatting.
Present a screen which provides a payment gateway to buy more time - or for less money - buy another drink.
I've been to cafes before which let you "rent" a security lock for laptops and all the tables had a loop which they could be attached too.
In many cafes I've seen signs saying "no tablets/laptops at the weekend" to make space for customers who want to socialise.