Sugar, syrup, and honey all end up doing roughly the same job in coffee, sweetening it, but they behave differently once they hit a hot drink. Here is how the main options actually compare.
White sugar
Neutral, clean sweetness with no added flavour. Dissolves reasonably well in hot coffee, less well in iced. The default choice for a reason, but it adds nothing beyond sweetness.
Flavoured sugar
Behaves like white sugar in terms of dissolving, but carries additional flavour, vanilla, cocoa, or fruit, depending on what it is made with. Because the flavour comes from real ingredients rather than a diluted liquid, it tends to taste more concentrated without adding extra volume to the drink. Good for stirring straight into a cup or dissolving into hot milk for a homemade latte.
Flavoured syrup
Convenient and consistent, syrup is what most coffee shops use for flavoured drinks. Its main drawback is that it adds liquid volume, which dilutes the coffee itself, and many commercial syrups lean on artificial flavouring to stay shelf stable.
Honey
Adds a distinct floral sweetness and a small amount of extra viscosity. Dissolves less easily in coffee than sugar, especially in colder drinks, and its flavour can compete with more delicate coffee notes rather than complementing them.
Maple syrup
A more assertive flavour than honey, with a slight smokiness. Works well in autumnal or spiced coffee drinks, less well as an everyday sweetener since the flavour is strong.
Agave syrup
Sweeter than sugar by volume, meaning less is needed, with a very mild, almost neutral flavour. Dissolves easily but offers little in the way of taste beyond sweetness.
Which one to actually use
For an everyday cup, plain sugar is hard to beat for simplicity. For something with more character, without the dilution and shelf-stable additives of a syrup, a real flavoured sugar like Dirty Vanilla or Midnight Mocha gives you that extra layer while keeping the coffee itself undiluted.