Same /k/ sound. Write K before i, e, ê, y, and C before every other vowel.
kẹo · kêu · kỳ · cá · cơm · con
ươ or ưa?
One vowel: written ươ when a final follows (nước), ưa when there is none (mưa).
nước · đường · mưa · cửa
hỏi or ngã?
Two different marks in writing (hook / tilde). In the South they sound the same: only knowing the word tells you which.
ngủ · phở · sữa · mũi
Quick answers
How do you pronounce cà phê sữa đá?
Block by block: a → c → ca → huyền → cà · ê → ph → phê · ươ → ưa → s → sưa → ngã → sữa · a → đ → đa → sắc → đá. Tone: cà: huyền (grave accent · low falling) · phê: ngang (no mark · level) · sữa: ngã (tilde · broken rising) · đá: sắc (acute accent · high rising). Read each block aloud, then compare with the recording, in a Southern or a Northern voice.
What tone is cà phê sữa đá?
cà: huyền (grave accent · low falling) · phê: ngang (no mark · level) · sữa: ngã (tilde · broken rising) · đá: sắc (acute accent · high rising)
Is cà phê sữa đá said differently in the South and the North?
South · Sài Gòn: s = x, ngã = hỏi. North · Hà Nội: s = x.