All natural and actually easier than using a powdered mix.

3/4 cup lemon juice
1 tsp liquid stevia (I used Whole Foods 365 brand)

1 empty 64 oz container (preferably glass as acids interact with plastic) with a tight fitting lid
Measuring cups
1 tsp measure

Put lemon juice in empty container
Put stevia in with the lemon juice
Add water until halfway full
Put lid on container and shake well.
Finish filling with water.
Chill and serve.

That’s all folks…just don’t use powdered stevia as it is really chemical tasting. The liquid tastes much better. You may want it sweeter. If you do, just keep adding stevia to taste.