For bog standard local pootles, there's always sweets in the bar bag - haribo and mentos mints.
Longer rides, then I'll lob an individually wrapped pain au chocolat, a packet of crisps and a banana into the pannier. Might not eat any of it, but it's there.
Away days on the bike, standard packup of a cheese and chutney sandwich, crisps, banana, tangerine and a pain au chocolat, plus a few extras like salted nuts, marmite rice cakes, dried fruit.
Don't bother with any of the "specialist" type stuff, and if I don't eat anything, back into the cupboard it goes. Also, I avoid taking chocolate bars as that can get a bit messy on warmer days.