Both. They are synonyms. Tomar also means to take.

Both "beber" and "tomar" mean "to drink" and can be used interchangeably. Note that "tomar" also means "to take" Tengo sed, voy a beber agua. Tengo sed, voy a tomar agua. Voy a tomar una foto del mar. Voy a tomar un taxi. :)

To drink is "beber" in Spanish but with some liquids we prefer to use "tomar" (in the same way as to have in English). We normally say "tomar un café" (to have a coffee) instead of "beber un café". In Mexico and some other Latinamerican coutriies, but not in Spain, "tomar" (alone with no substantive) is a synonim of drinking alcohol (beer, wine, etc).

Both means "To drink" In Venezuela if you say just "Voy a tomar" or "Voy a beber" means you are going to drink alcohol..

beber :-)