Here is a good, corrected version:
Camels can go a long time without eating or drinking. They use the fat stored in their hump for food and to help make water inside their bodies.
Why this is better (easy steps):
- Change and to or in the first sentence because the camel can go without eating or without drinking (or both).
- Say the fat stored in their hump to show the hump keeps fat.
- Say for food and to help make water because the camel uses the fat for energy (food) and when the body uses fat it also makes some water.
Extra note: Camels do not store water in their humps — they store fat. The fat helps them survive when food and drink are hard to find.