I don't think someone who offers Sprite in place of Mountain Dew is a "jerk" or anything - but they're not being helpful - in spite of any good intentions they may have.
From now on, if anyone goes someplace that says "We carry Coke Products", tell them you want a TAB. When they say they don't have it, get all upset and say "YOU SAID YOU CARRY COKE PRODUCTS! WHY DO YOU LIE TO ME?!?".
Or, if they have it, quickly leave... it's probably way past it's expiration date.