We have a Syrian but Im sure some of the same treats would go down well
Each day I put out his hamster mix in his dish, a very small piece of veg nearby, and an "extra" in a different part of the cage (he expects it to be there and runs to find it, then dives into a little hidey house near the treat to eat it). So I try and put a different veg out each day, usually broccoli, carrot, cucumber or a bit of green bean, or cauliflower. I end up buying more veg than we usually would, so keep it in the fridge - they last a long time then. Carrots last for ages in the fridge.
The extra is different each day as well - usually either a small piece of walnut, or pecan nut, or brazil nut or a couple of pumpkin seeds, or a tiny piece of cheese (only once a week with the cheese). He also has a Rosewoods naturals treat stick to chew on (they are sugar free so won't cause tooth decay!)
Cypher knows about seeds for dwarf hammies so her info will be good.
If he's out of the cage I'll give him a tiny piece of chicken (if we have any in) - plain cooked, not if it's been cooked in a sauce eg. Or any other cold meat we happen to have. Our last hammy had beef, pheasant, grouse and fish occasionally too! but I only give those fresh extras out of cage as they tend to eat them straight away and I'd worry they'd be hoarded and go off in the cage.
It's best to avoid sugary treats - especially with dwarf hammies as they are prone to diabetes. Pumpkin seeds usually go down well here. You can get little packs of them and nuts, in the supermarket. Most kinds of nuts go down well - but just plain, not salted. And almonds are debatable. I keep in plain cashew nuts, brazil nuts, monkey nuts in the shell, walnuts and pecan nuts. Trouble is I end up eating the nuts myself and having to buy more.