Donaldson begins his rehab today in A+. Assuming the Jays place him on waivers immediately upon the start of his rehab, he will clear waivers sometime on August 30th. That gives the Jays somewhere in the neighborhood of 24 hours to find a trade partner. It is not a coincidence that his rehab started today.
JD is owed roughly $3.8M rest of season, so it isn't exactly chump change to acquire him. I don't think anyone will risk claiming him, but a team might get bold knowing the Jays won't give him away to a claiming team, and will simply pull him back.
He is all but guaranteed to be given a QO, which will likely result in a pick around #75 for the Jays. Picks around #75 tend to be mid-range 40s, so the acquiring team would need to beat that value in terms of a prospect package to even get the Jays to consider trading him. In the case of the Braves, that means someone one the back end of their Top 20.
If the acquiring team wants the Jays to eat cash, and it seems like the Braves would need that to happen, they will likely have to kick in a 45, or multiple 40s.