Those were shots of tequila mixed with sparkling water, you had to hit the desk with the glass to get it foamy (and try not to break it) and drink it all at once while it's still foaming.
Phil Lesh & Friends The Dead Gov't Mule Warren Haynes The Allman Brothers Band Mountain Dave Matthews Band Buckwheat Zydeco Coheed And Cambria Jack Casady The Les Claypool Frog Brigade Bloodline The Derek Trucks Band Corrosion Of Conformity Dickey Betts Band