The most common and most likely answer to this crossword clue is the 4 letter word ICKY
I
C
K
Y
More clues leading to the result ICKY
Buddy explains!

The straight part
We know that "too sweet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case too sweet = icky.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ICKY mean?
ICKY adjective- Unpleasantly sticky; yucky; disgusting.
- Excessively sentimental.
- Unwell or upset; in a bad state of mind or health.