What other sources of caffeine are there other than black coffee and green tea? any tastier alternatives?

Caffeine: Caffeine is found in chocolate, many sodas, and many teas. There are some other less well known foods as well. But, caffeine is not necessary for life or the diet. I can think of no reason a 16 year old would even care or want caffeine given they do not need it. Caffeine is highly addictive.

No quick fix: At age 16 if one needs energy and a way to deal with anxiety, depression and hopelessness, one needs to seek good counsel not caffeine. A physician who will look at life style issues like sleep, exercise, stress management, exposure to passive smoke, and alcohol, and checks for low levels of vitamin d3, iron deficiency, low blood sugar, or low blood pressure may be able to help you.