Person A wants person B to drink the juice they made over two days, i.e. they don't want them to drink it all on the first day, and so they tell person B, "Drink this over two days". Can they also say, "Drink this over a period of two days"? Are both correct? Is there any other way to say this?
Yes, it is correct, over/during (a period of) two days:
One of the meaning and usage of over refers to:
- during something, or while doing something:
- I was in Seattle over the summer. Shall we discuss it over lunch/over a drink? They took/spent an hour over lunch (= their meal lasted an hour). It's fascinating to watch how a baby changes and develops over time (= as time passes).