adulterate
verb [ T usually passive ] uk/əˈdʌl.tə.reɪt/ us/əˈdʌl.tə.reɪt/
（在饮食中）掺杂，掺假
to make food or drink weaker or to lower its quality, by adding something else
There were complaints that the beer had been adulterated with water. 有多人投诉说这啤酒里面兑了水。