Como dizer "Dessa água nunca beberei" em inglês

Don't knock it until you've tried it. (to knock = to criticize)
Never say never.

Don't knock it until you've tried it.Nice one.Thankyou Thomas!

In Spanish with a slightly different meaning:

Dicen los de tu casa,
que ninguno me puede ver
Diles que no batan al agua
Que algún día la han de beber.

Your relatives say
that nobody can stand me.
Tell them not to muddy the water
because some day they will (have to) drink it.

desta água não beberei (fig.)
that won't happen to me

[A Dictionary of Informal Brazilian Portuguese]

You can't drink all the water offered to you. You could get "the trots" (AKA: turista, Montezuma's revenge, Aztec-two-step, etc.)