Depends on what you intend to do before, during, and after.
Me? I take plently of food to cook. Music or the guitar. Plenty of drinks other than liquor. Toilet paper and paper towels for those "emeregencies". A tent for when it rains. A folding stool.
Rarely do I hike in. If I have my druthers then I drive to the spot. That way I have music, a place to put up my valuables, and a place to sit (tailgate). Also in case of emergencies you have mobility. I like a good stream. Swimming and source of water. (Make sure if you use the water that you sterilize it). Sometimes I canoe in. Use the ice chest for a seat.
If you catch fish, you can bring a newspaper. Clean the fish, season with salt, pepper, maybe a bit of lemon juice. Wrap the fish in soaked newspaper one at a time. Through them on the coals and wait for the heat to steam the fish. Excellent.
I always have coffee and what ever those with me use in their coffee. I usually put it in ziplocks.
Of course if your trip is to get wasted then you may not need these things. Bring a good lounge chair and a tarp and nothing else but the ice chest in that case.