I really wouldn't recommend milkbones either. The only chemical in them that's verified is BHA, but even just a little is a big risk. Carcinogenic compounds (BHA) should really be avoided at all costs for the health of your hamsters. However, there's no need to feel down as there's tons of other options out there! Biscrock biscuits, whimzees, antos chews, and the occasional greenie (occasional as they contain gelatin) all make wonderful treats for your hamster(s) and are safe too. You could even offer homemeade dog treats if you're skilled in the culinary arts
Best wishes