H2O2 (Hydrogen Peroxide) catalysis in clear plastic bottle?
An easy test for this would be to react H2O2 with yeast or baking soda (sodium bicarbonate) before and after sun bathing. Or you could simply measure gas production in the sun vs in a box for say 24 hours.

An easy way to measure the O2 released is to use a closed vessel with a ballon, but the more scientific method uses an inverted, graduated column.



You can measure light intensity with a photometer.