The UFC said Fukada, who lost to a unanimous decision to Brad Tavares at the March 3 show in Saitama, tested positive for phenylpropanolamine, norpseudoephedrine and ephedrine, which are stimulants and banned substances.
Caceres tested positive for marijuana metabolites.
The UFC said he had been suspended for six months, would attend drug rehabilitation classes and will have to pass a drug test after his ban to receive clearance to compete again.
Caceres' split-decision win over Kyung Ho Kang has also been changed to a no contest.
"The UFC organization has a strict, consistent policy against the use of any illegal and/or performance-enhancing drugs, stimulants or masking agents," the UFC said in a statement Wednesday. "All 22 fighters on the UFC on FUEL TV 8 card were drug tested at the event and all fighters passed their drug tests with the exception of Alex Caceres and Riki Fukada."