Looks like adventures are only spent on mimics and turning the crank (which moves all barrels down a row and rotates in three on top). Tentatively looks like only row 3 items (schnapps etc, crappy spleen items, soda water, etc) are available.
By now i'm sure there's good info on the wiki, but I figured I'd point out that better items appear once barrels have been rotated out of the lowest row.
From the September 8 update, all the barrel mimics have been renamed:
Monster #177 has name 'mimic' but Manuel calls it 'tiny barrel mimic'
Manuel says that 'tiny barrel mimic' (177) has unrecognized image 'mimic1.gif'
Monster #287 has name 'mimic' but Manuel calls it 'small barrel mimic'
Manuel says that 'small barrel mimic' (287) has unrecognized image 'mimic2.gif'
Monster #288 has name 'mimic' but Manuel calls it 'medium-sized barrel mimic'
Manuel says that 'medium-sized barrel mimic' (288) has unrecognized image 'mimic3.gif'
Monster #289 has name 'mimic' but Manuel calls it 'huge barrel mimic'
Manuel says that 'huge barrel mimic' (289) has unrecognized image 'mimic4.gif'