Bought a bottle of Sprite walked out of the shack ...

Bought a bottle of Sprite walked out of the shack threw receipt in trash, the Sprite was expired in October. They offered to exchange it but every bottle in the fridge had expired. Asked for a refund they said I would have to go to guest services. Went there and they refused to give a refund without the receipt, guess I needed to dig in the trash and get it??? Wouldnt even give me another drink that the cashier threw away. I hate a thief and six flags took my hard earned money, call me petty but a Sprite at six flags ain't cheap.