I had a maple bacon shake at
Slater's 50/50 one time. It tasted like a vanilla shake with about a cup of maple syrup mixed in. I.e., not bacony at all and WAY too much maple. They offered to remake it with less maple. The second one had a nice balance of maply sweetness, but it still lacked any kind of bacon overtone.
A while back Jack in the Box had a limited-edition bacon shake which I rather liked.