garlic
蒜 centers on garlic as a plant, specifically its bulb or the plant itself.
蒜 combines the plant radical 艹 with 祘, which likely contributes the sound. The exact historical development of 祘 is uncertain.
The top 艹 suggests a plant, and the bottom 祘 looks like a cluster of bulbs. Picture garlic cloves growing under the leaves.
For サン, imagine the sun (サン) shining on a field of garlic, making the bulbs grow plump and strong.