@greyor A friend borrowed my K&R, so it's gone, too 😂
What specifically would be fun for you to write I'm not sure of, but you could perhaps pick something from these /g/ programming challenges. One of the things I've done in C to get back into it was a brainfuck interpreter.
https://git.echoz.io/chris/tbf
@Absinthe
I remember project Euler. That's a good idea for some fun, small projects to do.
@greyor