If you look up there are loads of treads about baby food and veggies etc in the past. I think that'll be the best info for you as everyone seems to have different opinions!
I personally give my Syrian tiny amount ( like 1tsp) of veg, fruit or herbs daily and she loves it. Her absolute favourite is basil leaf but she has parsley, dill and mint leaves and carrot, broccoli, grape, apple, blueberry, banana, avacado, Romani lettuce, cooked garden pea, sweet corn... I'm sure I'm forgetting some of the vegs. Also she has once a week 1tsp of Hipps organic breakfast porridge which baby food comes in jar. Also loads of hammy treats and some dog bonio and dog chews.
I'm sure I go over board about extra treats but hey hamsters lives are short and they spent it in limited small space we provide. So my thought is if I can make her food little interesting at least she experienced some sort of life
That is said as long as you don't over feed your hammy and end up with very fat one not only shorten their lives too!