I started out on a 25 mile each way commute about a year ago. Was in terrible shape before I started commuting.
The first time was a real bugger. Didn't actually make it the whole way. Had to call the wife to come get me with about two miles left.
Just make sure you have the right equipment. I jumped on a 15 year old mountain bike that hadn't seen the light of day in about 14 years. Original knobby tires and not one tune up at all.
After that first ride it took me about a week to recover. Meanwhile, I put 1.5" slick tires, got a tune up, and put a rack and a rack pack on the back. The second week was about 100% easier. I averaged about twice a week for six or so months until I found a job closer to my work. I was able to get the trip time down to about 1:30-1:40 each way depending on the headwinds.
I didn't worry too much about food/drink other than making sure my water bottle was full of water before starting out. Since you say you already have done the commute you should know what your limitations already are and what you need.