Final answer:
The sentence is grammatically incorrect because the possessive pronoun 'mi' should agree in number with the singular noun 'café'.
Step-by-step explanation:
The sentence 'A mí me gusta beber mis café por la mañana' is grammatically incorrect. The correct form should be 'A mí me gusta beber mi café por la mañana', without the plural 's' in 'mis café'. In Spanish, the possessive pronoun 'mi' agrees in number with the noun it modifies. Since 'café' is singular, the pronoun should also be singular.
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