If you're looking for fast food options, I also recommend Taco Bell, Dunkin Donuts, and Wendy's. Though, I'm sure you'll find much better food in the proper restaurants! Have a great time 

Blooms in Whitechapel, London's East End was the best place ever for bagles. Sadly no longer open.
And a Krispy kreme on every second corner.I had them every morning for breakfast.