From time to time I have a need to code after work. Sometimes I really like kicking off a new private project but I don't always have the right idea. I will then usually go to codewars and solve one, two or ten katas for fun. As a C# developer doing mostly high-level stuff I enjoy learning the deep basics of javascript or php (you can bash php but I like it). Sometimes, when doing a C# kata, I even learn how to solve things differently than I'm used to.

Either way I grow when doing those small tasks.

Tip: If you like competition you can take a look at codingame's Clash of Code which is a 15min coding competition with others.