In the UK we have a product called Bug Grub which is a dry food designed for feeding to crickets. I feed mine Bug Grub, and a mixture of carrot ends, carrot peelings, apple cores (pips removed, they contain cyanide), melon skins, and the occasional grape, depending what is available. They also have a quarter od kitchen roll folded up and wet available to them too, so they can have dry food, ater and/or fruit/veg.
Regardless of whether it's eaten or not, I remove and replace the fruit or veg daily to try to prevent mould - also keep it seperate from the dry food and the water.