Bananas, dates, figs, papayas, persimmons, pears and some varieties of grapes are all non-acidic, sweet fruits. Prunes and raisins are examples of non-acidic dried fruits, although it's important to note that even though prunes are considered non-acidic, fresh plums fall into the category of sub-acidic fruits.
There are also a number of non-acidic fruits that are less common in the western world, such as jackfruit, longan, mamey sapote, mangosteen and jujube or Chinese date.
Fruits are typically put into one of four categories: acid, subacid, high fat and sub-acidic or sweet. Sometimes melons are also put into their own category, although the majority of them have a very low pH level. This includes watermelons, cantaloupes and honeydew melons. Most varieties of grapes fall into the sub-acidic category, although sweeter varieties like Muscat or Thompson are considered non-acidic.
The fruits in the high-fat category are also typically considered non-acidic, but they are grouped together due to their high fat content. This group includes avocados, olives and coconuts. On the other end of the spectrum, citrus fruits generally have the highest acid content, as they contain ascorbic acid, also known as vitamin C. Of these, lemons and grapefruits tend to have the highest level of acid.