Dog Shake (aka Root Beer)

I know everyone is on a health crusade nowadays! I am trying to make an effort myself, but I still enjoy a bit of pop (yes, I realize I am 1 of 4 people who still call it pop - even in the midwest).
This particular kind is referred to as "Dog Shake" around here. Awhile back my son saw it at Arby's when getting a drink and picked out "Dog Shake". If you cannot read, that is quite the logical guess! I should probably clear things up for him before someone's child teases him...kids can be quite snotty to one another, where do they learn that from...tv?
Anyway, since I am pregnant no caffeine is good and diet as I do not need the calories. I am not thinking about the "artificial sweetners"....
It just tastes quite delicious (cannot even tell it is "diet"!).