Radical 口
12 strokes
mouth 口 (5) + a drink 曷 (575b) = to drink 喝
[喝酒 (102) hējiǔ to drink wine/liquor]
[喝汤 (531) hētāng to drink soup]

They leave a drink (imagine a glass of beer) by the mouth of the cave to see if anyone will come out to drink it. / They’re hoping to catch sight of the giant who lives there as a hermit.