On fruit, vegetable, food Fruit, food, vegetable, under what circumstances do not add s? I like eat fruit or I like eat fruits?

On fruit, vegetable, food Fruit, food, vegetable, under what circumstances do not add s? I like eat fruit or I like eat fruits?

I like eating fruit
Vegetable is countable, food, fruit is not countable nouns, but when it means species, it is countable