As stated on Wikia, the original joke is about "serving coffee for ghouls" and "man on a (baseball) base". The original script goes like this:
"Serving coffee for ghouls" and "slow-footed man on a (baseball) base"... is "to refrain from tourui".
Here, tourui is either 糖類 (saccharides; sweeteners) or 盗塁 (base stealing; steal; stolen base), which basically means:
- Not consuming sugar on coffee for ghouls
- Resist stealing a base for slow-footed man
Since this Japanese wordplay is almost impossible to be translated properly (and the joke itself is quite technical), I believe the translator changed it so that joke can be understood easier while trying to preserve the nuance for "sweetener/sugar" and "serving coffee for ghouls".
... as for the meaning of "sugar" in the translated version, it probably means: