I tnd to buy small bags of 'fancy' hay with added flowers and bits, but on a day to day basis just use regular meadow hay, which I buy in 20 kg sacks.
As far as fruit and veg go, my lot love (to varying degrees) peppers, cucumber, mange tout, green beans, coriander (although it took a while for them to acquire the taste) parsley, apples, watermelon, carrot, lettuce (not iceberg) and kale.
But their absolute favorite thing to eat is fresh grass with the odd dandelion leaf thrown in.