Either find food in the wild or spawn in some food and then eat it.

I have tried this on my own server using only CF+VPP admin tools to check values, The same results were seen on a vanilla server I started just to test this, I also joined another server that was vanilla and after sprinting until I ran out of food then eating a single mackerel steak, the food values were comparable. One venison steak, baked, allowed me to sprint for over half an hour before I ran out of food again.

During testing, I used admin tools to set my food and water to 0 just before eating the food. I waited until my character had absorbed the food and I saw down arrows on energy and water, I then looked at the character in the VPP Admin tools player manager and noted the energy and water values. Here are some example results :

mackerel baked food 1136 water 186
mackerel dried food 600 water 0
mackerel boiled food and water both 800
carp baked food 900 water 300
carp boiled food and water both 750
carp dried food 600 water 0
tin beans food 799 water 399
cereal water 0 food 959
cow steak baked food 1421 water 235
cow boiled food 1246 water 496
cow dried food 1246 water 0
chicken boiled food 107 water 63
chicken baked food 200 water 37
chicken dried water 0 food 187