For taming treats I use pumpkin seeds or these Rosewood little hearts
https://www.amazon.co.uk/Rosewood-Na...+little+hearts
For healthy cage treats I also give half a walnut (shelled) or half a brazil nut (shelled). I cut the brazil nut in half and eat one half first because sometimes you can get a bad tasting one! If it tastes ok I put the other half out for him. So maybe a nut twice a week. If he's extra lucky he gets a piece of fresh coconut - I get the little packs of fresh coconut pieces from the supermarket. Very occasionally a small piece of cheddar cheese, and sometimes a small piece of apple (no pips) without the skin, or a blueberry or a small bit of strawberry. They love anything fresh.
They can be funny with monkey nuts - it can help if you start it off and make a bit of a hole in the shell as a lazy hamster will give up trying to crack it open. Newt went off them quite quickly though.