I get very motivated to program things in pointless sandboxes, like ComputerCraft, Fancade, Logo (programming language), Geometry Dash. This might train my brain and teach me some basic concepts like SoA vs AoS (fancade, but accidentally), network architecture (ComputerCraft), but I'm also not really sure what to do for relevant reality topics.
I also do codegolf.stackexchange.com which has some pretty cool challenges.