I'm 12 hrs post op and Doctor wants me to drink 48 oz clear liquid. I'm have a hard time drinking, it takes me a hour to drink one cup, I have a lot of gas that I am burping.

Take your time dont force it. Just remember to take sips as often as you can. I was told to drink 2oz every hour and no more than that for the first 24hrs

I also have been sleeping quite a bit, which makes trying to get the amount of liquids down harder. But each time I wake I feel small improvements

Continue on your path, slow and steady. If you still find you cannot get the amount of liquids down that are required in a couple of days, you should call you doctor. You don't want to get dehydrated. That happened to me because I was too full to get in the required amount and I ended up back at the hospital for a few days shortly after my surgery.