If you don't have any ideas of what to make, get a blank page & start making marks. Do whatever you feel like.
It may turn out cool, but even if it doesn't, you will have woken your brain up.
If you "don't have any ideas", then do random stuff. Try things. Mess around.
Exercise your creativity.
Don't wait for inspiration. Inspire yourself.
At least for me, nothing fills my brain with artistic ideas in the same way that dedicating time to making things even when I "don't have ideas" does.