Impossible! All alcohol turns into straight sugar as soon as you drink it! To keep sugar as low as possible, drink it straight on the rocks! After bypass the alcohol goes straight to the blood, so be cautious as you really cant drink as much as before. The ratio is 3 to 1, for every 2 oz of Alcohol u consume ( 2oz is standard measure for a shot and for the other drinks) , your body gets the affect of 3 -2oz shots..... So be careful.
Suggestion, crystal light has mix drink flavors, take some with you and ask bartender to make your drinks with it instead of the syrups they normall use, u can also ask for half the alcohol.
Or, just have then give u just crystal light but in a mix drink looking presentation so everyone has the impression you are drinking right a long with them. That's what I do...I still have just as much fun and so far every bartender I've asked has no problem doing it, especially cause I tip as if it's n alcohol drink !