The general word for sugar, white, brown or rock. Chinese cooks also add it to savoury dishes, and Shanghai cooking mixes it into soy sauce, so braises there come out slightly sweet.
Left-side rice radical - the indexing component, marking the food/grain origin of sugar. Early Chinese sweeteners were grain-based syrups (麦芽糖, malt sugar from barley) long before cane sugar reached the country, so any sweetener was filed under 米. Same family: 粉 (powder), 粥 (porridge), 粽 (rice dumpling).
Right-side 唐 supplies the sound táng - a clean phonetic match with no tone shift. No semantic link to the Tang dynasty, but a useful mnemonic since cane-sugar refining did spread across China during Tang-era trade with Southeast Asia. Same phonetic group: 塘 (pond), 搪 (evade), 膛 (chest cavity).