全糖 is the default 100% sweetness on the bubble-tea sugar scale. Compare
七分糖 (qīfēntáng, 70%),
半糖 (bàntáng, 50%),
三分糖 (sānfēntáng, 30%),
微糖 (wēitáng, slight),
无糖 (wútáng, none). Most learners settle on
半糖 once they realize
全糖 in China is genuinely sweet.