Google Games Like Quick Draw. You can either draw something new from scratch, or open some file and just play around with it. The order in this selection is not absolute, but the best.
Join other players talking about games. This simple sketchbook supports many different formats like png, jpg or svg vectors. What do 50 million drawings look like?
Drawize is a fun and free online drawing game like skribbl or online pictionary!
App as one of the many artificial intelligence. Be quick because time is limited, but you have to make sure the ai can understand what you're drawing, that helps you overcome the challenge. Uses a neural network to try to guess what you are drawing. Afterall, everyone has a piece of artist in himself.