zu wenig Kontext. Ein mögliche Übersetzung ist 'bester Hörplatz'.

Der Punkt, wo die Relation zwischen Aufwand und Ertrag am besten ist.
würde das in den Kontext passen?

native UK speaker:
".. you may see the A300 as the sweet-spot of sensor and features"
aus einem Vergleich digitaler Kameras:
www.cameralabs.com/reviews/Sony_Alpha_DSLR_A200/verdict.shtml

Als Kurzform der Übersetzung ist "Optimum" immer gut. Abhängig vom Kontext gibt es sicherlich auch besseres.

I am familiar with the expression from tennis. The middle of the tennis racket is called the sweet spot, which indicates the best place to make contact with the ball. So in most contexts, I would think "optimal/optimum" would probably be appropriate.

The expression is also used to express fondness. Example: I have a sweet spot in my heart for red-headed children, meaning that I am particularly fond of them.

I've also heard it used in business. Example: "The gaming industry formerly targeted young males. Today, women 35 and older are considered the new sweet spot."
This is a bit more difficult to translate into German, but I believe the meaning is clear from context that women are the new target group for gaming products.

Hope this helps.