"go to the beach" is more grammatically correct. So it is important to put "the" which is referred to as an article in English grammar. The use of "the" is used to describe or point out the noun

Go to beach (incorrect) Go to school (correct) Go to hospital (incorrect in American English. Correct in British English) There’s no reason or logic. It’s just that ‘school’ (and ‘hospital’ in the UK) have developed a meaning without an article.

If you are talking about a particular beach, then you will use "the beach". If you are talking about just any beach, then you will use "a beach". I don't see a use for "go to beach" because there is an article missing.

Go to beach is incomplete. I mean unless you were telling someone in complete frustration because they keep asking you over and over again « where should we go ». Exhausted you would say « go to beach »