As far as I am aware there is no specific single or generally accepted term used for the fiscal compensation in sugar arrangements. Sometimes they are described very directly/clearly as fees or payments or money, but more often some euphemism is used. Examples I've hear include "allowance", "support", "help", "consideration", "benefit", "donation" etc, and often these nouns are preceded by the adjective "sugar", e.g., "sugar allowance". Sometime just the word "sugar" by itself is used, although this can also refer to the physical sugar, not just the fiscal sugar, so to speak.
There may well be some Japanese term or terms that is/are used in enjou kosai situations, but I don't know what they are if there are any. Japanese generally makes extensive use of euphemisms, so my guess is that there are one or more.
-Ww