Best Vitamin Powder for dogs?

[bossynbella]

I have for the last two years given our dogs a couple teaspoons of vitamin powder every day with their food, I just mix it up with the dry food as well as a cup of water and their Glucausomine (sp?). I had always bought what we sold at work (wal-mart) but now they changed what they carry to a pill form which I am having no fun trying to get the dogs to take. I realize with the good food they get they probably don't NEED it but I would still like to give them some. I was researching the last few days and there are just so many and of course they all sound great on their websites. So do any of you use one? If so what?

I have a 5 year old Black lab, a 5 year old Shepherd mix and a 3 year old Beagle. I plan to just buy some online, next month.

Thanks
Melissa