You can sponsor the child while you're still overseas as long as you're demonstrating an attempt that you're going to move to Canada to take up permanent residence. In declaring that sponsorship intent, and in submitting a sponsorship application, even if the child is stateless and needs a travel document to be able to travel to Canada, we will issue a single-journey travel document to facilitate the travel to Canada, because the ultimate intent is clear. The intent is to sponsor the child as a permanent resident and put her on that track to permanent residency and citizenship.
As for arrival in Canada, because for a minor who's under the age of 18 the normal three-year window period of waiting to apply for citizenship does not apply, you can apply immediately upon arrival in Canada for citizenship for the child.