Can I become a chef without experience or do I need to have worked in a restaurant?

You don't need any previous experience to become a chef

Ok great

Yes you can,you no need any prior qualification to became a chef in the ARMY, You spend spend 18 weeks phase 2 at the Defence Food Service Wing at Worthy Down. First, you'll learn about food and personal hygiene. Then you start working in the kitchen where you have the chance to earn a Level 2 qualification in Health & Safety. Training ends with four weeks of field catering, including five days learning Basic Close Combat Skills.

Here you find more information

https://apply.army.mod.uk/roles/royal-logistic-corps/chef