Hi Lilipip - I've got a few Multys and have had similar problems. I don't rate the Sippy at all to be honest. I've also got a couple of bottle bandits (chewers!) so I'm in the process of putting hanging bottles in each cage now which seem to work really well. The hams can drink quite easily from them but they can't grab hold of the bottles for chewing and pushing/pulling off.
I use the bottles with a hook in the top, thread the wire through the hook and then just feed the wire through the bars at the top so they swing if you follow. Hope that helps a bit. Oh, and you will need to block the original bottle hole or you may find your hamster chews round the hole! I use a large bolt with two washers, one inside and one outside