Even if a product's bottle is too dark or not transparent, you can still track it using Nectar. Rather than mark the level visually, simply input the level in hundredths, which correlate to percentage left.
- Find the product you'd like to audit
- Tap the input box directly beneath the bottle image
- Input the approximate level in hundredths (0.32 = 32% remaining)
- Tap anywhere outside the input to close the keyboard and continue auditing