Contrary to popular belief that sketching can take hours, there are ways to actually make it simpler and fast.
Whether you are wanting to communicate an idea to a set of people to support your pitch, whether you want to save a memory of something infront of you, quick sketching is an interesting way to record and communicate your thoughts. You don't need a lot of mediums and can make do with whatever you can find. A ball point pen, a stub of a pencil, charcoal, anything!
ProTip: I generally carry a small blank paper notebook, slightly bigger than the traditional phonebook. A handy pen and I'm all set!