Yeah, you can do that. Figure one tub of Crystal light will flavor approx 3 liters of water.
Hmm, ok this is more difficult than I expected.
Figure if you are using a 500ml water bottle when you work out, and you want a total of 10 grams of BCAA, you would need an additional 1/6 of a tub of crystal light. That woud be about 1 tub per 60 grams of BCAA.
Multiply that out for however many grams of BCAA you bought.