I am usually asleep, need all the beauty sleep I can get, but if not then, in no particular order one or more of the following: thinking, worrying, suffering from hideous indigestion, being sick, answering the door to policemen!
This morning I made an egg mc muffin at 5 am, it was delicious. Now eating foods I haven't had for years and I'm enjoying every bite. Everything is just a good as I remember it. Haven't had any ice cream yet, I'm afraid to go that far. Have to have some small pleasures in life even if it's only food.
If I've napped and that's the reason I'm up in the wee hours, I'm probably watching TV and crocheting. If I wake up and can't go back to sleep, I usually try reading, or I go on line and if both of those fail, I watch TV and crochet.