Harry Hamster seems to be the most popular for Syrians but Rupert never really liked it, so I would have a few different brands on the go for him and this seemed to work the best, he liked variety!
I always added a sprinkle of jumbo oats to his food and he liked the occasional piece of nut (brazil, hazel or cashew - all plain), dried pasta, dog kibble and millet.
He got fresh food every day as his tum seemed perfectly able to cope with it - I'd aim for veg six days, and fruit just once a week. Broccoli was his favourite but he really liked peas, carrot, sweetcorn and spinach too