I am having one rlly bad rn 💀💀💀💀 but usually trying drawing challenges, recreating screenshots, someone else's art in your own style, draw someone else's oc, draw a meme with ur own characters, humanize something that usually works for me <3 or try drawing some things u never draw like a skull or something, maybe u can try some anatomy studies just to warm up. I don't really enjoy doing them but they help u warm up ur wrists so u can draw something better later. I also often use pinterest for ideas, you can try to recreate a pic from there :) be it with an oc or just draw the person on jt

when I'm feeling particularly burnt out I try and turn my attention to a hobby i've never done before/haven't done for a while!

my go to burn out activity is flower/leaf pressing since all you need to do it is a thick book, a few sheets of computer paper, and somewhere nice to walk around :D
I also find that lurking around second hand stores for cool things and hands on activities seem to do a lot for me (like planting some flowers or rearranging my bedroom furniture!). Doing stuff that isn't too creatively focused can feel suuuper refreshing!