When the speaker compares the sun to a toddler, the feeling the simile suggests is that the toddler is bright in personality, and happy as well, to add extra details. The toddler is sweet as candy, - (putting another simile in here) and as nice as a summer day.
*Explanation:*
**The sun is known for happiness and brightness, and it is what makes people say “It is a nice day today!”. When some speaker states that a —— is as —— as the sun, they are meaning that this —— is bright, glad, kind, and delightful!**
Hope this helped!