Ginger biscuits are good...but our pony LOVES the mini gingerbread men from Asda bakery...36 for £1.50 for so. We buy them for ourselves but he always has some of them. (Preferably with a cup of tea in an ice cream container.) He also likes carrots, apples, parsnips, Polos and Tic Tacs. Not to mention "herby" treats of all sorts. My son's old pony loved honey & lemon Lockets.
Buzz likes bannanas and buy him badminton high fibre feed but feed it as a treat much cheaper than the tiny little bags of herbal horse treats and he LOVES them.
Milly loves a polo. If i have a thermos cup with coffee goes mental trying to get it of me, funny cause she doesnt do it with any other drink..........i occasionally let her lick the cup when i have finished but she really doesnt need caffine she is quite nutty enough!