Add more and more meaning and quality …
Sketchnotes are about increasing the quality of your notes and about fun. Also because fun and creativity helps remembering things. So it is very useful. Adding emotions to some parts of your notes can be very helpful in this sense AND it adds information. Imagine something you wrote down as a fact, you might add “I take it as a fact”, “whisper, noted between the lines” or “I don’t agree, it makes me angry”. A graphical element is often faster, easier to get and more beautiful.
And there is an easy way to do so.

its a fact! straight lines, bold letters

Whisper โ dotted line

Angry โ pointy speech bubble if you distribute dots around, even more powerful

Thoughtful โ cloud with question mark

Cloudy โ cloud as a speech bubble

Very cloudy – express with more deferring cloud items
Of course you can use the same style elements on any other icon, not only on text boxes. Play around, while you are drawing and see some more elements next page.