Set oven to 420F.
Whisk together the first 7 ingredients in a large bowl until smooth.
Add the slices of bread to the batter, one by one, and let each piece soak for no more than 1 minute. Soaking too long will cause the bread to fall apart.
Set a nonstick skillet on medium heat and lightly spray with cooking spray or olive oil.
Add 2 or 3 slices of soaked bread, and be sure not to crowd the skillet. Cook on each side for approximately 1 minute, or until the edges are brown and slightly crispy.
For meal prep, place the slices on a baking grid or a baking sheet lined with parchment paper. Bake in the oven for 5 to 7 minutes.
Remove from the oven, then allow the slices to cool to room temperature. Add parchment paper between the slices, then store each portion in a sealable plastic bag.