Japanese speakers
Mistake: Pronouncing it as "ENDO APPU" with a full d release and separated syllables.
Why: Katakana English preserves each consonant with a supporting vowel.
Fix: The d of "end" links directly to the [ʌ] of "up": [ˈɛnˈdʌp] or with flap-d [ˈɛnˈɾʌp]. Say "endup" as one word.
Korean speakers
Mistake: Producing clear released [d] and glottal reset before "up".
Why: Korean prosody adds glottal onsets to vowels.
Fix: Link the d directly to [ʌ]: [ˈɛnˈdʌp]. In American English, the d may flap: [ˈɛnˈɾʌp]. Both natural.
Spanish speakers
Mistake: Producing Spanish-style [ð] between vowels.
Why: Spanish d weakens intervocalically.
Fix: English d stays firm (or flaps to [ɾ]): [ˈɛnˈdʌp]. No Spanish [ð] weakening.