The Sound of Gulping
ごくごく (gokugoku) is the onomatopoeia for drinking something down in big, eager swallows. It mimics the “goku, goku” sound your throat makes when you gulp — the sound of a thirsty person draining a glass of water, a cold beer, or a carton of milk in one go.
ごくごく belongs to the giongo (擬音語) category, the onomatopoeia for real, physical sounds. Unlike a quiet sip, ごくごく is audible and rhythmic, evoking the satisfying glug of liquid going down fast.
When to Use ごくごく
Use ごくごく when someone drinks quickly and heartily — usually because they’re thirsty or the drink tastes great. The common pattern is 「ごくごく飲む」 (to gulp down). For a single big swallow, Japanese uses ごくっ (gokutto) or ごくり (gokuri); the doubled ごくごく means the gulping continues swallow after swallow.
Fun Fact
There’s a classic ritual after a Japanese hot spring (温泉): standing with one hand on your hip and drinking a bottle of cold milk ごくごく. The combination is such an iconic image that beverage ads lean on the ごくごく sound to make a drink look irresistibly refreshing.
Examples
In Anime
Restaurant to Another World (異世界食堂)
Patrons gulp down their drinks ごくごく with visible relief, part of the show's loving focus on the joy of eating and drinking.
Laid-Back Camp (ゆるキャン△)
After setting up camp in the cold, the girls drink hot and cold beverages ごくごく, making every sip look incredibly satisfying.