"Longer" runs - when to take a snack & what?

[Chocolateteabag]

I've been slowly building up my running distances over this year - I normally run first thing and cannot eat beforehand. I've not had a problem up to about 12k but found the last couple of long runs (14 & 18k) I was getting low. I'm trail running so slow and hilly
Guess I need to think about taking something to eat with me but:

What should I take?*
When in the run do I take it?

*I do take a small water when I'm running over 10k but normally drink it at the end when I'm cooling down. Don't think I could chew on something massive that will sit on my stomach like a banana

Any advice?

I take Nakd bars and just have a niblble sporadically after 10k.
I used to use gels, but for some strange reason they contain sweetners (which is stupid in a product soley designed for a quick energy fix) and I tended to suffer after the run.

I have a belt with two bottles, fill one with water and the other with squash.

Yep- nakd bars are great.
Jelly babies?
I'm not a fan of gels either.
I tend to run roads, so take a card to buy water instead of carry it.

Thankyou both, will have a look at Nakd bars!

I like the veloforte bars or ote zesty orange bars when I go trail running. For a drink I will have a rehydration tab such as high 5. I've tried gels but can't seem to find any I like.