Prednisone also gives me insomnia, so I used to stack my pillows up and stay in bed but propped up until it was time to go to work - it helps a teensy bit to use gravity in this situation - I also completely cut out additional sodium and only ate whole foods (rice, quinoa, tofu, veggies, bread, etc) - I couldn't eat at all when I was sick and so cut out all meat & dairy and that seemed to help also. I am trying to do that now but don't want to go comepletely vegan then go to dinner with friends and splurge and make my stomach have a meltdown.
Someone suggested water pills, which I am not going to do. I have to take enough unnatural things to stay well (for which I am thankful but it's obviously not ideal) so don't want to take anything else.