De or het reservepotje?

The correct Dutch article is:

het reservepotje

Rule Diminutives (-je, -tje, -pje): always het. See the rule

How to use reservepotje

the reservepotjehet reservepotje
this reservepotjedit reservepotje
that reservepotjedat reservepotje
our reservepotjeons reservepotje
your reservepotjejouw reservepotje
every reservepotjeelk reservepotje
which reservepotje?welk reservepotje?
a big reservepotje / the big reservepotjeeen groot reservepotje, het grote reservepotje