We have invested a fair amount of time to try to get sales tax treatment on food items in our California stores correct. But the rules are insane. Beyond all the crazy rules (e.g. if a customer buys a refrigerated burrito it may be non-taxable, but if he puts it in the microwave in the store to heat it up it becomes taxable for sure) is the fact that sometimes customer intent matters (e.g. will they consume it at one of the picnic tables on site, or take it back to their home or camp site)
When searching for more resources on the topic, I found this flow chart on deciding if CA sales tax applies to food
Here is more, from the same article
Under California law, foods eaten on the premise of an eatery is taxed while the same item taken to go is not: "Sales of food for human consumption are generally exempt from tax unless sold in a heated condition (except hot bakery items or hot beverages, such as coffee, sold for a separate price), served as meals, consumed at or on the seller's facilities, ordinarily sold for consumption on or near the seller's parking facility, or sold for consumption where there is an admission charge." Exactly which type of foods do and do not fall under the scope of this provision is the frustrating devil in the detail.
Eskenazi notes a few of the ridiculous results of drawing an artificial distinction between hot and cold foods. "A hot sandwich to go would be taxable," for example, "While a prepackaged, cold one would not -- but a cold sandwich becomes taxable if it has hot gravy poured onto it. Cold foods to go are generally not taxable -- but hot foods that have cooled are taxable (meaning a cold sandwich slathered in "hot" gravy that has cooled to room temperature is taxable)."