For the bottles and pots, clear ones are good if you can get them so that children can watch them filling up. I use bottles from hotel toiletries and sample sized bottles, and there is also a Kinder egg inside in there too - it's nice to provide a range of sizes and openings. The screw top bottles can be difficult for a toddler to open, but keep an eye out because once they have mastered this skill then none of your bottles in the house are safe! Everything can be scooped up in to the bag easily when you've finished.
Obviously this activity is best for an older toddler that will not put any of the small items into their mouth, and even older children should only play under supervision.
You might also like my other toddler busy bags:
Make a monster busy bag kit
Threading busy bag
Christmas busy bag