There’re observation decks, open air terrace, public spaces up there. And it’s free! Though you’ll have to make an advance booking.
There’s an option to book a table at one of the Sky Garden’s bars/cafes: Skypod (great cocktails), Darwin or Fenchurch Seafood. You’ll get a table for 2 hours as well as the access to Sky Garden.
Celebrating 1 year in London:
There’re a great view of Shard, Thames, Canary Wharf, City of London, Isle of Dogs, Tower Bridge and The Tower of London from up there. I’ve spent 2 hours enjoying the view and sipping the drinks up there, and already booked the next visit.