mi - my possessive determiner all genders singular for 1st person singular
mí - me pronoun 1st person singular. If you know about grammar, it is not the nominative, accusative or dative case, but the prepositional case.
Examples of this last case:
- Move it towards me. // Muévelo hacia mí
- [Who likes icecreams?] Me! // ¡A mí!
As you see, it is used after a preposition.
Tú (you 2nd person sing. Informal) bebes. Él, ella, ellos, usted (you sing. formal) (3rd person sing. or 2nd person sing. formal) bebe. Ellas, ellos, ustedes (3rd and 2nd person plural) beben.
Then there is also Yo bebo. Nosotros bebemos.
And in Spain: Vosotros (2nd person plural informal) bebéis.