If you asked me this question 5 years ago, I would of said a flavoured BCAA product like Xtend.
Now that I am older and care more about my health and longevity, I try to limit artificial flavours, artificial colours and artificial sweeteners wherever possible.
My go to BCAA supplement now is a capsulated BCAA supplement that contains no artificial additives. The supplement I am currently using is gear from n2bm.com. Works great and pretty affordable.