In preparation for the second bimonthly tapdancing competition, Squidward made a change to his diet/exercise regime. The latter went up; the former went down, up and out.
Before, he'd just stopped eating altogether. This time, he tried a different approach: keeping food in the system for exactly three minutes before up chucking in the nearest bathroom. His throat was drenched by the effects of the bulimia, but he didn't care.
He was punishing his body for only getting third place last time, and showing it what would happen if it failed again.