yes to food/snacks, no to liquids (so no drinks) in your hand luggage. You can, however, buy juice etc in the shops etc after you've gone through security.
Check your airlines FAQs for what you can and can't pack (and in which quantities) in hand luggage. If you're flying Easyjet, remember your hand luggage is one item only per person, so you need to be able to pack your handbag, camera bag etc etc etc in your one hand luggage bag for boarding the plane.