You can use vinegar for fleas on puppies since the flea products are much too strong and toxic for puppies. Straight white vinegar applied with a cotton ball works well since you can apply without getting it near their eyes and nose.
Warm it a bit if it’s cold. The puppies don’t seem to mind the smell and it makes their coats soft.
I’ve also used Tea Tree Oil in water to kill fleas for puppies and dogs. You can find directions and many other uses for Tea Tree here:
http://www.theherbsplace.com/teatreeuses.html
You can find quality 100% pure Tea Tree Oil here:
http://www.theherbsplace.com/teatree.html