I usually go for 70% sugar — full sugar is too cloying.
Tips
culture
Chinese tea shops typically offer a fixed sugar ladder: 全糖 (100%), 少糖 (70% or 'less'), 七分糖 (70%), 五分糖 (50%), 三分糖 (30%), 微糖 (slightly), 无糖 (none). Health-conscious customers usually settle on 三分糖 or 五分糖.
grammar
X分 (fēn) literally means 'X parts out of ten'. So 七分糖 = 'seven-parts sugar' = 70%. The same pattern applies to ice: 七分冰, 半冰, 去冰.
