Disappointed

I bought a 2litre coke on the 27th December at ShopRite savoy, it happened that when I open it didn't give me a sound that it has acid. I tasted it but it didn't have taste or acid. I returned it this morning but the manager in charge said there's nothing he can do cause I didn't have the slip. Shoprite savoy must do better and must keep records cause not everyone can keep slips.