too old but thirsty

We stop in a small village off the #40 between Quebec City and Trois Rivières so I can buy myself a drink. Small village, small corner store. Potato chips in an array of powdered flavours and a wall of refrigerators stocked with beer. There's only one small cooler near the cash with power drinks and soft drinks. And okay, there's apple juice, but I don't like apple juice.
I pick what I think will be the best of the worst.
The young woman at the cash has magenta hair she's painstakingly tousled and gunked into place. She squints at the can I've set on the counter. Only kids buy that, she says. Seulement des jeunes qui achètent  ça.
We both keep looking at the can. She makes no move to ring up the purchase. Is she not going to let me buy it because I'm too old? Should I tell her I've got a kid in the car?
I pull a $5 bill from my old-lady snap change purse and hand it to her so she has to make change.