Hundreds of people climb Kawah Ijen every night and literally NONE of them do this!
40 minutes' drive from Kawah Ijen takes you directly to brilliant hotsprings where you can relax, shower, and recover after your big hike. I cannot think of a single reason why you wouldn't want to do this after spending the night hiking.
Visit the 150 year old De Djawatan Forest, snap some amazing pictures, climb a tree, and ride a horse & carriage
Two beautiful waterfalls half way up the volcano - one is a complete hidden secret
The Terracotta Dancers of East Java - this is a cultural heritage site built to preserve the art of Gadrung, a traditional dance
Climbing Mt Bromo for free (without a guide)
Secret sunrise spots
Order to see the sunrise and visit Bromo crater - without the crowds