There is Croquis Cafe (which is a youtube channel) and I took the Schoolism course on Gesture drawing which was pretty good--it comes with a bunch of gestures built in, and it has a series of lessons by a great teacher if you don't really know the ropes. https://www.schoolism.com/lp/gesture-drawing-alex-woo/ It costs money, though (and the price went up, I took this when it was 15$ a month. The lessons are short enough you only need to buy one month. Way cheaper than other industry art classes that are 400$ each.)
What I like doing in non-pandemic times is to sit at a cafe or library and sneakily draw people out of the corner of my eye. Nowadays there's still the option of going to the park and drawing people walking by. It naturally gives you a pretty short time limit. Plus, you'll get really good at drawing people's dogs.