Mainly we did two things: short project and brainstorming (reverse brainstorming).
(1) short project
We went through discover and design phase with temporarily newly formed team in a short time. In this mini project, we also went through observation phase quickly, defining problem framing, assumption, and hunt statement. Additionally, to make the new team, we did an exercise lining ourselves ordered by age without talking. I think it was good idea to warm up ourselves.
(2) reverse brainstorming
Coming up with different (sometimes, negative) or apposite aspects for one theme. I think it is useful to identify what the service/product should be improved.