Sorry, but that solar brew is a risk.

If you do like using solar energy that way, heat that batch of liquid to at least 195 degrees for a couple minutes to kill off bacteria that loves to grow in that warm broth.

BTW, making a simple syrup, infused with lemon and mint, is the way to sweeten any good iced tea.

2 parts sugar to 1 part water, bring to a boil and then let it cool. While cooling you can add flavors like a couple sliced lemons and some crushed mint leaves. Strain into a container and it will keep in the 'fridge for a couple months, but don't worry, it won't last that long.