Using some and any can be confusing! It is not difficult to learn how and when to use them. The rules are simple, see below. It just takes practice to use some and any correctly.
Things can be counted. We call them Countable Nouns. Examples: students, books, pencils, dogs, flowers, kites, bananas, cars, apples, teachers, and etc.
Things cannot be counted. We call them Uncountable Nouns. Examples: sugar, dust, water, jam, flour, syrup, salt, coffee, ink, sand, air, money, tea, juice, oil, butter, and etc.
Some is used in affirmative sentences for both countable and uncountable nouns. Examples; There are some tomatoes; there is some water at campsite.
Any is used in negative and interrogative for both countable / uncountable nouns. Examples: There aren’t any matches, There isn’t any juice, are there any carrots? Is there any rice?
There are many more exercises for some and any here: http://agendaweb.org/grammar/any_some-exercises.html