Hi. Are you in the UK? This would help members advise on which food and beddings to use.
First of all, your step-daughter should have made better provision for her hamster leaving it with someone! Dear oh dear....she did`nt leave any food or instruction?
Never mind though, your in the right place for advice!
Trouble is, if you don`t know what he`s been fed on, changing his diet suddenly could cause him tummy issues, but two of the best hamster mixes in the UK are:
Burgess Supahamster Harvest. This is a lovely, muesli type mix and all the hamster needs in terms of a daily meal. A good tablespoonful a day is plenty, but don`t overfeed if he`s only picking at it. They do a dwarf mix aswell but if he`s a syrian, you just want the normal mix.
Supreme Harry Hamster: Another mix that readily available in pet shops. Larger extruded biscuits than the Burgess mix but fine all the same. I prefer the Burgess mix though because of the variety it has.
Hamster don`t NEED meat, so if he`s not used to it, don`t feed it. Especially as he`s an older hamster and meat will be higher in protein which he does`nt need at his age.
The Flax bedding (is it Aubiouse?) bedding/litter should be fine for him. I use a mixture of Aubiouse and shavings just now, but mainly aubiose.
Bedding should just be paper based. Ripped up plain white toilet roll sheets will be fine. I would`nt give him hay or straw incase these jag his eyes or pouches.
You can offer him a small piece of apple (remove the pips first) as hamster enjoy a little piece of apple.
Don`t go mad with other fruit and vegetables though if he`s not used to these as they can give him an upset bowel.
Hope this helps in the meantime.
Oh and hamsters (especially syrians) like to sleep all day, so I would leave him alone through the day to snooze or he may be angry if woken up. Hamsters mainly like to play in the late evenings.