Pumpkin baby food? Sweet potato might also work.
Just wanted to check - when you say he hasn't eaten, pooped, or drank much "today" you mean during the night, right?
It's normal to pee at the same time as they poop. Half-green is also half-brown! I would assume stress until it's been a week or so.
Was his pee extremely yellow and stinky, or light yellow and only a little smelly? If you're worried about the amount he is drinking, I would put him on white/light colored liners and look for pee stains. My pig's litter liners are white fleece and it's extremely reassuring to see that yellow circle every morning.