As you level up, different types of sour pinatas will begin to plague your garden.
Simply check your journal for the residency requirements of those pinatas. Meet those requirements and the pinata will change into it's standard version and become a resident. At this point, you'll obtain the corresponding Tower of Sour piece for that pinata. As long as that piece of the tower is activated, you won't have any of the sour version of that pinata coming into your garden.