Somewhat healthy cakes??
In addition to Mani's, Diamond Bakery on Fairfax offers some sugar-free goods, as well as will do custom orders.
Zen Bakery on Pico works with juices - I'd call and see if they can do something for you.
You could also do an ice cream cake from The Bigg Chill using frozen yogurt.
Viktor Benes', Bristol Farms and Ralph's have sugar free baked goods; I'd contact the first and see what they could do for you.
Depending upon how far you want to travel, Fortune Bakery in San Gabriel has a good selection.
Does vegan count as healthy? If so, try Jamaica's Cakes on Pico in West LA. They almost always have at least a few vegan mini-cakes and desserts in their case, as well as vegan cupcakes on the counter. I had a coconut cupcake (an overrun from a customer order) from there about a week ago and was very impressed.
11511 West Pico Blvd, Los Angeles, CA 90064