There are a couple of things to avoid feeding him, however, any kind of citrus food as their high acidic content will give him a tummy upset! You should also avoid fried food, and avoid dramatic changes in their diet.
Hamsters love Fruit and Veg
Small amounts of fruit and vegetables a day are best if you wish he will also happily eat small pieces of meat or foliage from the garden, but his diet is not dependent upon it. Dry food should always be his main source of food and for this reason, should always be available to him. Some of the best foods to give him include bean sprouts, broccoli, cauliflower, celery, cucumber, dandelion leaves, grass, peas, sweet corn, apple, banana, grapes, and melon. Birdseed is also an acceptable supplement to your hamster’s diet! Of course in the wild, he would also have access to insects, which are an excellent source of protein. You could substitute this with dry cat food, cooked chicken or turkey, scrambled eggs.
Try your Hamster with a custard cream Biscuit “Small piece only”
Most hamster-specific products from the pet shop or supermarket will fulfil many of your hamster’s dietary requirements; there are normally multiple varieties on the shelf to tick all of the boxes. It is very important to stay clear of sweets and chocolates, what is a treat for you and me is highly toxic for a lot of animals, and hamsters are included in this! Malted milk-based biscuits are good as a treat, as well as custard creams, digestive biscuits, cheerios, walnuts, hazelnuts, cashew nuts, and brazil nuts, though make sure they are all unsalted. Your hamster will also like raisins and sultanas and cake-like carrot cake. Remember that it is important to rinse fruit and vegetables before feeding them to your hamster! Last but by no means least is water, hamsters don’t normally need to drink much, especially if you are feeding him fresh fruits and vegetables. He does still need a fresh supply of water that has either been filtered or boiled and cooled down, this is because there are various chemicals in tap water that are harmless to us but toxic to him.