The drink you order shapes what tapa you receive, though the relationship is not always explicit. Bars adjust what they send based on a rough judgment of who's at the counter and what they're drinking. A caña (small draught beer) at 9pm tends to come with a more generous plate than a soft drink at 3pm.
Caña — the default first drink in any Spanish bar. Roughly 200ml of draught beer, €1.80 to €2.50. Most bars give their better tapas with a caña because it is the local standard. Ordering a caña signals you know how bars work; ordering a pint or a cocktail at a tapas bar signals you don't.
Tinto de verano — red wine with lemon soda over ice. The Granada summer drink. Lighter than beer, longer-lasting, and genuinely what locals order from May through October. More refreshing than wine on a warm evening, and it pairs comfortably with the full range of tapas from jamón to gazpacho. Order it by name; asking for sangria is a tourist marker.
Copa de vino — a glass of house wine. Standard across most bars, though the quality varies widely. At bars with a proper wine list (Taberna La Tana in the Albaicín is the reference point), worth asking what's available before defaulting to the house pour.
Non-alcoholic drinks — soft drinks, water, and coffee also come with a free tapa in most Granada bars. The tradition applies to the drink, not the alcohol content. Asking explicitly when you order is fine; it's not an unusual request.