@Alvarito987 "A lot of water" "lots of water" "loads of water" (uncountable) and "a lot of apples" "lots of apples" and "loads of apples" (countable) all sound absolutely fine to me.
However if you are talking about a single large apple you could say something like "that's a lot of apple" (referring to the volume of the apple). This one doesn't work with lots of/loads of for me.
In fact referring to water in a similar way - "that's a lot of water" - needs "a lot of", but you can use lots of/loads of in other contexts e.g. "there's a lot of water on the floor" "there's lots of water on the floor" "there's loads of water on the floor" are all absolutely fine.
The only thing I can think of where one works and not the others is the "that's a lot of X" construction. And of course as I said before "loads of" is more informal.
Also, just to note as well, "that's a lot of apples" when talking about lots of apples also works - it doesn't have to be singular. But that construction works when saying a singular object is very large. "That's a lot of X" also usually expresses surprise at the size/amount of something