Diet Coke has, like, 30 mg of caffeine, half of what a cup of black tea has. If you are worried about the stress levels, take L-Theanine supplements instead (sa

Diet Coke has, like, 30 mg of caffeine, half of what a cup of black tea has. If you are worried about the stress levels, take L-Theanine supplements instead (same active ingredient as tea). While reducing your overall levels of caffeine consumption is probably good, the important thing is to keep your levels consistent.