This shop used to be feasible when they did not indicate that you must do the drive thru first. I could go in, rushing right to the restroom as if it were an emergency and then settle in the dining area "waiting for my friend", impatiently looking at my watch and out the window. Once my 10 min had elapsed I could whip out my phone and have a pretend phone call, saying "Where are you???" After a few minutes of silent "listening" I could say, "Ok." and with the phone still to my ear, leave the store and go to my vehicle. These places usually had their parking in plain view of the store, so the fake conversation would continue as I got in the vehicle. Then almost as an afterthought I would pull through the drive-thru.
Although it would be odd, you may be able to reverse the process, make your purchase and then with the beverage in hand, enter the store with your cell phone stuck to your ear having a fake conversation about meeting somewhere that has you delaying your departure for that location for 10-15 min.
Another trick is to take along a small container of water which you dump on yourself looking like a beverage spill that you hurry inside to the restroom to "clean up". You do the dump just as you are at the end of the drive thru road where the cameras aren't watching and then turn into the parking lot to park in front of the door. When I'm doing this one, I usually use the napkin from the drive thru order to be blotting at myself. Take your time in the restroom as the 10 minute clock started when you came in the door. Make your notes while running the water like you were rinsing out the spot. If they have an air hand dryer run that for a bit. Emerge with a still damp, slightly larger spot, but at a leisurely pace to look around and maybe even ask a few questions if the place isn't busy--like the price of a bag of coffee or the mugs or if it is a combo DD/BR, what kind of ice cream is that?