90%
I consider my diet high protein. I get 120 to 140 grams per day, on my 1200-1600 calorie a day diet it comes to about 40% depending. I've found this ratio to suit me well, after quite a bit of adjustments over the past 11 weeks.
If you're talking fast food, burgers with no buns or grilled chicken with no bun, I guess would be a decent option. If you're talking restaurants, it would be much easier. Although with fast food, idk how realistic 90% would be considering how much fat is in everything.
If you try 90%, do post! I'd be very interested to see how it goes!