Negative keywords help prevent ads from appearing on shopping results pages that don’t meet your campaign objectives. Negative keyword targeting can be used at either the campaign level or ad group level. (From Amazon Ads Advanced Tools Center)
Discuss how to utilize the Search Term Report (STR) to add negatives when you’re creating discovery campaigns (Auto, Broad, and Phrase) where you’re launching keywords sometimes we have to add negatives for the keywords that aren’t performing so that we stop spending money on them and the other keywords can continue to spend money profitably.
For example: Electrolyte Powder that's triggering for all of these different keywords.


Open the Search Term Report.
Click Enable editing.
Add filters by hitting Ctrl+Shift+L or go to Sort & Filter then click Filter.

For Campaign Name [Column E], choose one product (at a time).

For Match Type [Column H], hide Exact.

For 7 Day Total Sales [Column I], filter to only show $0.00 (no sales).
Sort Spend [Column N] from Largest to Smallest.

Highlight the rows with high spend (based on your criteria) but no sales.
There are different extents of spending. Usually, you can cap it at half of the price of your product. If you have a $28 product, anything above $14 and no sales or you can even go less and say $10 and no sales then highlight the $10 and no sales in light red.

Remove the filter for 7 Day Total Sales [Column I].
Sort by Total Advertising Cost of Sales (ACOS) [Column P] from Largest to Smallest.

Highlight the rows with high ACoS (based on your criteria) and no sales.
Let's say about 50% ACOS and no sales.

These limits are totally up to you and you can always start with looser limits like above 80% or 90% and no sales, above $15, above $18 and no sales, and then you can get tighter and tighter and tighter. If you start too tight, you might kill your sales. So start a little bit loose and then work your way tighter until you figure out what works the best.
Update the filter for Total Advertising Cost of Sales (ACOS) [Column P] to filter by color and only show your chosen color for the highlighted rows. The report will now only show you the:

These keywords will be added as Negatives. To do this, take note of the: