As said, too much can cause upset tummies, its very high in sugar and can therefore upset their natural gut flora. Mine get it very rarely, and when you hand it to them you have to be so, so careful or they'll take your fingers off, they love it, and probably would live off it, if they could.
My mum gave them some once whilst I was at school, but her portions are big, and I notcied squishy poos, hence I knew she'd done her usual king size portion. Thankfully she has now trimmed it down as I threatened to hide the shed keys! :lol: :lol: