Sparingly means using only a little at a time. Use it sparingly, applied sparingly, spend sparingly.
It appears most often in instructions — on medicines, on strong flavours, on anything where more is worse. It implies deliberate restraint rather than shortage. Note spare, in the sense of to hold back, which is what the word comes from.
1adverbsparinglyUsing only a little at a time.
“Use the salt sparingly; you can always add more later.”
sparingly is a manner of using.
From sparing + -ly.
Etymology from Wiktionary, CC BY-SA