Koko Black are offering free hot chocolates for the 1st 20 people at each location nationwide (except QVB). Opening times vary between locations but usually between 8AM-10AM.
They are also offering this crossover of a Lune Croissant and Koko Black chocolate. That's not free though and likely will be sold out.
Also remember to get your free chocolate frog from Haigh's.
Koko Black seriously make the best hot chocolate ever. Can't go past it everytime I hit the CBD.