I design board games for a hobby, maybe sometime soon as more of a profession. A silent car does wonders for me to come up with ideas for coming up with ideas for my game designs. Walking the dogs and a long shower also work well. Between all three of them, they're probably responsible for at least 50% of all the creative ideas I've had over the years.

Really quiet or electronic music can work too though. It's people talking or singing lyrics that makes thinking difficult for me.

Pretty similar to coding, actually, except you're mostly stuck in front of a computer for that.