if you try the text to speech of Google translate the difference is HUGE: https://translate.google.es/#da/en/sukker%20og%20sukkeret So I'm not sure wether the sound in this example is right or wrong...
I'm not a native speaker. I have the same question as you.
The IPA for "sukker" is [ˈsɔɡ̊ɐ] /sokər/, but I could not find the IPA for "sukkeret"
On www.forvo.com, you can get the audio of the words "sukker" and "sukkeret" but the words are spoken by two different Danish persons.
The difference is subtle to my ear (native N. American English). It sounds as though there is an extremely subtle "l" on the end of "sukkeret".
On another discussion page, someone said that it sounded like "Soogle", with the "s" sounding like a gentle "z".
As an AngloDane, here's my take: The "kk" needs to be softened, approaching "gg" but not quite there, sort of in between... The "et" at the end needs to be so soft that it's hardly there, just heard as a tiny echo. Think "ed" rather than "et" but the tongue doesn't touch the teeth or go near them. A miniscule "eh" tacked on the end. Just a tiny tongue movement which changes the whole word into 3 syllables. Agree the audio is lacking in quality.
Merel, that's mostly an issue of English, since Danish generally doesn't make a difference between simple and progressive forms. Usually, if you're talking about a specific event, you'll use the progressive form in English ("I'm eating salad for dinner"), and if you're talking about a habit, you'll use the simple form ("I eat salad every evening"). It's both just "Jeg spiser salat" in Danish.