Well, I think you already know the answer to this one. Transparent bottles of any kind tend to be worse at keeping the product stable compared to for example, medical amber glass or non-transparent airless bottles. But, what can you do providing that you really don’t have the choice?
-Add some EDTA, BHT, mixed tocopherols and proper preservative to your formula
-On label explicitly leave a note to keep the product away from direct sunlight
-Use non-transparent label and make so it covers most of the transparent package (believe it or not this actually helps in a great manner) and
-Leave the product in intented package 21 day at room temperature and on direct sunlight. Observe what happens with and without the label, with different amount of antioxidant and etc.