シロップ

しろっぷ
noun
syrup
food
1. syrup; sweetened liquid
A thick, sweet liquid made by dissolving sugar in water, often flavored. Used in drinks, desserts, shaved ice, and as a sweetener. Also refers to medicinal syrup.
シロップを入(い)れすぎた。
I put in too much syrup.
I eat shaved ice with syrup poured over it.
At this cafe, you can add your favorite syrup to your coffee.

From English "syrup." Used broadly for any sweet liquid — from flavored syrups for shaved ice (かき氷(ごおり)) and coffee drinks to medicinal cough syrup.

Common collocations

Cultural note

In Japan, ガムシロップ (gum syrup) is the standard sweetener served with iced coffee. At かき氷(ごおり) stalls, colorful flavored syrups (いちご, メロン, ブルーハワイ, etc.) are a quintessential summer experience.