leavings / remnant / leftover / residue / dregs

(of the way in which liquid is drunk) in one gulp / (of the way in which liquid is drunk) in one swallow

(of the way in which one drinks a liquid) in one swallow / (of the way in which one drinks a liquid) by downing it / (of the way in which one drinks a liquid) in one gulp / (of the way in which one drinks a liquid) at one go

(of the way in which one drinks a liquid) in one gulp / (of the way in which one drinks a liquid) at one go / in great gulps / (of the way in which one drinks a liquid) in one swallow / (of the way in which one drinks a liquid) by downing it

swallow down / gulp down

drink at a gulp / (drink) in a gulp

drink at a gulp / in a gulping manner / gulp down

reduce / cut down / discard / dispose of / reduction / cut / throw away

promptly / quickly / quick / prompt / speedy

with dispatch / quick / prompt / speedy